From what I understood in the original post, the deck with which the debated hand was played was short 1 card. This was discovered as the next hand was being shuffled/prepared/dealt, when an extra card with the wrong colored back was discovered. In this scenario, according to RRoP, the hand played with the missing card should stand as played.
As an aside, any hand played with an extra card which is dealt is a fouled deck and all money is returned. Any hand played with an extra card which remains in the stub is fine, and no money is returned.
Several people have concocted scenarios where a player "inserts" a card with a different colored back into a deck/their hand in an attempt to freeroll. This won't work, because:
1- If a different colored card is discovered (i.e. dealt) during a hand, the deck is fouled and all money is returned, so there is no freeroll.
2- If the different colored card is inserted into the deck such that it is never dealt and it remains in the stub, then it didn't affect the hand anyway, and it doesn't invalidate the results of the hand either, so it is not a freeroll.
3- If a player knows the deck is fouled and doesn't say anything, their hand is dead, so they cannot freeroll.
Quote:
5. A player who knows the deck is defective has an obligation to point this out. If such a player instead tries to win a pot by taking aggressive action (trying for a freeroll), the player may lose the right to a refund, and the chips may be required to stay in the pot for the next deal.
4- If a player somehow has an extra card(s) in their hole cards, regardless of what color the back is, their hand is dead, so there is no freeroll.
5- If a player is caught inserting or removing cards, or otherwise cheating, they will probably get permabanned anyway.