Hi Mark:
If SB goes all-in and it is called by UTG, once all betting is complete, both hands must be shown. It is not a dead hand simply because he attempted to fold, and the dealer should not muck the cards. Assuming the cards are clearly retrievable and identifiable, the Dealer should return the cards to the SB and ask the SB to turn them over, since he is all-in and was called. This is to protect other players in the tournament (e.g. otherwise, it would be too easy for the SB to 'dump' chips to his friend UTG).
TDA Rule 11: Face Up for All-Ins
All cards will be turned face up without delay once a player is all-in and all betting action by all other players in the hand is complete.