What would the ruling be?

[smarterthanyoda]

This came up in a hand a saw last night. It ended up not being an issue, but I was just wondering what the rule would be in something like this...

At the river, there were four diamonds on the board and 2 players left. One player bet and the second called. The bettor showed a set. The caller looked at his cards for a couple seconds before throwing them face down towards the middle of the table. As soon as he had done this, his buddy watching from the rail said, "So you didn't have a diamond." The caller instantly grabbed for his cards, and got to them right after the dealer had started to pick them up. The cards were sitting right where they had landed, with the dealer's hands on the cards and the caller's hands on top of the dealer's. The dealer let go, and the caller picked up his cards again. It turned out he didn't have a diamond and the bettor won anyway.

My question is, what would have happened if the caller did have a diamond? Did he fold by throwing his cards away, or was his hand still live?