Here is the info from Robert's Rules of Poker...
1. Your hand is declared dead if:
(a) You fold or announce that you are folding when facing a bet or a raise.
(b) You throw your hand away in a forward motion causing another player to act
behind you (even if not facing a bet).
(c) In stud, when facing a bet, you pick your upcards off the table, turn your upcards
facedown, or mix your upcards and downcards together.
(d) The hand does not contain the proper number of cards for that particular game
(except at stud a hand missing the final card may be ruled live, and at lowball
and draw high a hand with too few cards before the draw is live). [See Section 16
- “Explanations,” discussion #4, for more information on the stud portion of this
(e) You act on a hand with a joker as a holecard in a game not using a joker. (A
player who acts on a hand without looking at a card assumes the liability of
finding an improper card, as given in Irregularities, rule #8.)
(f) You have the clock on you when facing a bet or raise and exceed the specified
2. Cards thrown into the muck may be ruled dead. However, a hand that is clearly identifiable may
be retrieved at management's discretion if doing so is in the best interest of the game. We will
make an extra effort to rule a hand retrievable if it was folded as a result of incorrect information
given to the player.
3. Cards thrown into another player's hand are dead, whether they are faceup or facedown.