[bav]

This is going to depend on the house rules. If the rules state that cards tossed face down over the betting line are dead, then fine, he loses; most rooms don't have that rule. Some rooms have a rule that if the dealer touches the face down cards after they are tossed in they are dead; most do not have such a rule. Some rooms have a rule that if a player's cards touch the board cards, they die; most do not.

This is one of those cases where there is not a single correct answer. The answer depends on where you were playing.

If you ask "what SHOULD happen" we start a whole new debate.

If you ask "what happens in most places", I haven't played in enough different rooms to know what the standard is around the country and around the world.

If you ask "what happens in most Vegas rooms", then the cards remain alive and the player can retrieve them.