I did something like that recently. I have top pair, no spade and the board shows four spades. I lay my hand down and say, "I don't have a spade." Now a guy about to throw his hand away looks back and finds a spade.

Bill Smith, World Champ of 85 and I played a lot together when we started out. Once the board had five spades. He showed me a trey of spades, a spade lower than anything on the board and I threw my hand away.