If player 1s hand is irretrievably mixed in the muck the pot has to go to player 2. Player three needs to be warned about acting out of turn (if he has already been warned then it may be time to stop inviting him since there really isn't anything else you can do to him.)

If the cards that player 1 had are clearly identfiable then give them back to player 1 and let player 2 act. (I do not subscribe too the magical muck theory that just because cards touched the muck they can't be retrieved). Clearly Player 1's mucking was caused in large part by Player 3's action and Player 1 should be penalized because Player 3 can't follow the rules.