How about this example where I think I know the answer, both holes cards must be used in the room I play in:
Player One A
K
Player Two 7
8
Flop of 9
10
J
Turn or River brings the Q
Player 2 flopped a straight flush to the J that was beaten by a Royal, but as it lays Player 2 now has a Q high straight flush using only one card in his hand.
I'm guessing the ruling will be Player 2 has to use the best 5 cards to make his hand and just got pretty unlucky.