Thus, the correct and most obvious remedy is as follows:
1) Give the hand back to the player on the button. He is to be warned/reprimanded/whatever for not protecting his hand. He will learn from the mistake.
2) Return the chips to the small blind player. Tell him to pay closer attention to action in the future.
3) The action is on the button player.
Tournament continues; everyone will be happy with that resolution, and it is fair to all concerned. There's no possible angle shoot out of this, and thus, it is reasonable to do this.