1) At worst both players are chopping the pot. 2) At best Seat 4 (SB) is getting their bet returned and losing the right to all previous called bets. Both rules referenced, #13 and #56 have no bearing here. They do not address pushed pots.
I think the last point identifies the big problem here - as you say, the rules don't address pushed pots specifically. On the one hand, you have an explicit rule that says "If a player does not fully table his cards, then mucks thinking he has won, he does so at his own risk. If the cards are not 100% identifiable and the TD rules that the hand could not clearly be read, the player has no claim to the pot", which may or may not apply, and on the other hand, you have ... well... a "practice tip" that most people have heard of but has not been explicitly reflected in any rule book (I may be mistaken but I don't think I've seen any actual "rules" regarding pushed pots, although perhaps we should have one).
Thomas, when I first read your answer "DISAGREE Completely", it sounded like you were suggesting that the SB should be awarded the whole pot. But your option #2 has the SB effectively losing the pot anyways, so I don't think it is that much different from what the others have agreed on. Whether SB should get a "penalty" of the "called" 4K is at least debatable.
Correct. I'm glad I saw this thread and wish this would have been able to be addressed at the Summit. This subject matter has way more weight IMO than most of the other subjects that were addressed. It's definitely a sore spot with me due my first hand experience. It's one thing to have the dealer swipe your unprotected cards and lose out on a pot because of both player error and dealer error combined. It's a whole different situation to have the pot pushed to you, you receive the chips and then release your cards after accepting the pot and then have it taken away from you because the dealer failed to see that some other player hasn't protected their own action. There's a thread that I can't seem to find where I advocate that the dealer is in fact part of the action. Meaning that when the dealer raps the table, that is your clue as a player that all action has been concluded for that betting round. Speak up of forever hold your peace and lose your right to act. There's also another reference I saw
So I'm in no way in favor like you and many others, of letting the SB win the hand in this spot. However, I'm not in favor of complete and total collateral damage either. The only reason the SB doesn't have cards is because the dealer pushed the pot to them. So the only options available here are a refund of the called bet, which many folks would go crazy over I'm sure or to chop the pot, which a whole other group would go crazy over as well. But which is the least damage to both players who didn't do anything wrong. The person in this equation who did anything wrong is our Dealer. So why are we penalizing any of the players?
This is not the same as the Gail Baumann situation where the player threw his cards in thinking he won the blinds and the TDA felt compelled to address this in Rule #13. It's completely different.
This is a situation where a bet was called verbally, heard by two players, but not the whole table and not even the dealer, nor were there any chips pushed into the pot to make the call. The player by the posters own account was still counting chips and had made no motion to the pot. How can we in good faith hold accountable the person who got pushed the pot for not knowing that another player had cards? When you get pushed a pot you are in full faith that all other players have folded. That's just common instinct.
I don't like the "chopping the pot" solution. I think that's just a cop out to avoid making a difficult decision. In addition to the discovery of a fouled deck, I think chopping the pot should generally be reserved, in theory, for very extreme situations -- possibly where the house has made a huge error and both players are completely innocent. I'm not sure that's the case here.
So you agree with me, that Chopping the pot is the best option. You say it here yourself in bold. The dealer is part of the house. The dealer works for the house. The dealer is an instrument the house employs to control the game. You know by most of my posts here that I'm no advocate for placing blame on the dealer in 90% of my posts. The players are to be held accountable too. But for me, in this case. I just don't see it.
To be clear, if there is evidence that an opponent hid his cards or that the cards were otherwise not in plain view, and that contributed to everyone at the table believing that the hand was over, then I actually would have no problem with even awarding the SB the pot as pushed in some cases. That certainly would seem to be defensible and in my view, fair. I would therefore not expect that the dealer has to check for all cards under the rail every time (that sounds pretty dramatic)... but I think both the dealer and the players have an obligation to follow the action and be reasonably certain that all action in the hand is complete before accepting the pot.
Again... you agree with me, although you try to persuade yourself from it

My actual hand was as follows - I'm in Seat 7 in BB. Everyone folds to Seat 5 and Seat 6 who limp for the call. I check and see the flop. I flop a full house. We checked and see the turn. Seat 6 checks and I bet (amount is irrelevant). Seat 5 calls, Seat 6 calls. River. Seat 6 checks. I bet, I get engaged in conversation with Seat 8 and 10. Pot gets pushed to me. I give the dealer my cards. Dealer mucks the board and begins to scramble. Seat 6 says "Hey I have cards". Everyone freezes in disbelief. How is this possible? What do you mean you have cards? We all look and see that he has both hands completely covering his cards. He lifts his hands and shows that in fact there are cards under them.
Just so I'm clear, how would you have ruled in your own situation? Would you have awarded yourself the pot or would you have returned your river bet and awarded seat 6 the remainder of the pot?
In any event, this is a much different situation. There does not seem to be any doubt that the cards were hidden. It is safe to assume that no one at the table could have reasonably verified that there was still action to be had.
However, poker is a visual game -- if an opponent's cards are in plain view, and especially if the called chips were put forth in plain view, I believe players have a responsibility to know what that means... there is still action pending. Could I accept the possibility of returning the SB's last bet in questionable situations? Perhaps. Would I award the SB the pot just because it was pushed to him? No way.
In my situation I would have given myself the pot!! What self proclaimed poker player would give up any portion of a pot voluntarily? None. (KIDDING sorta). I would have give myself the pot. In my situation two things were really clear. There was a bet, in clear view (a giant stack of chips). Dealer had looked for other hands, did not see any, pushed the pot to me, I released my hand, dealer mucks the board and begins to scramble. It was not until this moment that the player with cards spoke up. Whats a reasonable time allotment here? How long does a player have in order to protect his hand. Is it before the pot is pushed? After the pot is pushed? Before a dealer begins to scramble for the next hand? Is it after the dealer begins to scramble? How long do we give him before his action is void? I mean, by all accounts assuming I would get a shot at the pot, it be in my best interest as a player to never fold my hand. Just wait for the dealer to push a pot and start to scramble and then say "Hey, I have cards" and win every pot uncontested.
I don't particularly like chopping pots either, but sometimes you have to ask yourself what is fair, pushing someone a pot simple because they have cards, when they haven't called all bets and the pot has been pushed, is absolute craziness.