Nick alluded to the fact that: "The TDA mission is to increase global uniformity of poker tournament rules." The TDA does not include rule distinctions for cash games. On the other hand, Robert's Rules of Poker v11 (RRoP) covers rules for both cash games and tournaments. However, there is much in common with the RRoP and TDA rules, especially in the question that you have presented here.
There is the technical aspect to be considered given the written rules. Both sources speak to the matter of tabling cards at showdown for a winning hand:
TDA 2017 v3 - Tabling Cards & Killing Winning Hand
Rule #13
Part A: Proper tabling is both 1) turning all cards face up on the table and 2) allowing the dealer and players to read the hand clearly. “All cards” means both hole cards in hold’em, all 4 hole cards in Omaha, all 7 cards in 7-stud, etc.
Part B: At showdown players must protect their hands while waiting for cards to be read (See also Rule 65). Players who don’t fully table all cards, then muck thinking they’ve won, do so at their own risk. If a hand is not 100% retrievable and identifiable and the TD rules it was not clearly read, the player has no claim to the pot. The TDs decision on whether a hand was sufficiently tabled is final.
Part C: Dealers cannot kill a properly tabled hand that was obviously the winner.
RRoP v11 - Section 3 - General Poker Rules - The Showdown
Rule #1 - To win any part of a pot, a player must show all of his cards faceup on the table, whether they were used in the final hand played or not.
The TDA describes "Proper tabling" and makes clear that the TD "decides whether a hand was sufficiently tabled" and says a dealer cannot kill a properly tabled winner.
Taken literally, RRoP requires a winning hand to be tabled correctly with all required cards. "... a player must show all of his cards faceup on the table ..."
So, what about your scenario? What about a hand that was a clear winner (100% identifiable) that was improperly tabled? Both sources provide for this as well.
TDA 2017 v3 - Floor Decisions
Rule #1
The best interest of the game and fairness are top priorities in decision-making. Unusual circumstances occasionally dictate that common-sense decisions in the interest of fairness take priority over technical rules. Floor decisions are final.
Section 2 - House Policies - Decision-making
Rule #1. Management reserves the right to make decisions in the spirit of fairness, even if a strict interpretation of the rules may indicate a different ruling.
A TD has to ask themselves: Is it fair to award the money to a losing hand because the winning hand (100% identifiable) was mishandled (not strictly tabled properly)?
IMO: Both the TDA (tournament rules) and RRoP (cash and tournament rules) on fairness are provided so that we can override the technical rules in this case. Give the chips/cash to the winning hand.