This one made me rub my brain a bit. First our rule:
35: Action Out of Turn
Action out of turn will be binding if the action to that player has not changed. A check, call or fold does not change action. If action changes, the out of turn bet is not binding and is returned to the out of turn player who has all options including: calling, raising, or folding. An out of turn fold is binding.
So here's the gag.
NLHE, late in the tournament, 4-handed
SB is in seat 10, BB in seat 1, UTG seat 2, BUTTON seat 9.
Preflop SB BB and UTG all call. BUTTON folds
On the flop the dealer motions to the BB to start the action
BB puts in a large bet
SB shouts to stop the action.
Here's where it gets fun. The dealer says sorry I thought you folded but it was in fact the button. The SB says I am going to check anyway. Normally this would bind the BB's bet. The BB says "The dealer motioned to me first and I thought the SB had folded"(remember where they are seated) "I don't want to bet now". The dealer says that the bet must stand if action has not changed to that bet. BB does not like it and calls for a TD. Ruling?