I know the rules here, but is there a time that you would not strictly enforce them in your favor for the sake of being a good sport?
In the sixth round of a seven round Swiss, my team is one of four in contention and we are playing another team in the mix. On the second hand, I picked up:
Partner opens a strong and forcing 1♣, eventually shows a balanced 17-18 count and ends up declaring 3NT. I judged that the other table, using standard methods, would end up in the same contract. Declarer's black suits being irrelevant to the question, his red suits are:
Opening leader starts with a fourth best ♥ from a five card suit. Declarer ducks twice and, after taking the third ♥, leads a small ♦ in the hopes that the ♥s are 4-4 or that his RHO has the A♦.
Not lucky this time. The opening leader jumps up with the A♦ and cashes the fourth ♥, his partner showing out. As he is pulling out the setting trick, the card catches the 5♠ in his hand and it lands face up on the table before he can lead the last ♥. The director was called and ruled that, since the ♠ card was exposed to his partner, it is considered played. My partner wins this and quickly wraps up 9 tricks in a contract he should be down in. So, lucky after all.
We blitz the round, helped by a 12 IMP pickup on this board. Had we pushed the board, it would have been a near blitz, so the result was essentially the same and this would not have changed the final result (we finished 2nd).
Since I was dummy, I didn't say that much about what happened to my partner, I realize that the director ruled correctly and partner was just accepting the ruling, but had it been me declaring, I wonder if I would have been generous and told my LHO to play the ♥ as he intended; the contract should really be set, as it was at the other table. I've reflected on this, and I can't say one way or the other.
So, what would you do in this case? For the sake of good sportsmanship, would you tell your opponent to take back the card or would you follow the rules to the letter?
PS: it is exactly for things like this that I keep my hand below the level of the table when I play. A card falling to the floor cannot be seen by my partner.
Plus... it's free!