Good morning Big Al,
Did all other players fold before the dealer dealt the flop? Or, did the dealer prematurely deal while there were players yet to act? Also, were the three cards dealt such that the card that should have been burnt is clearly identifiable?
If all action was complete and the remaining two players are all-in before the flop was dealt then the solution is quite simple. The goal is to keep the board as accurate as possible while resolving the situation. If the missing burn card is clearly identifiable in the flop, then it simply becomes the burn card and the forth card off of the stub completes the flop.
Depending on the answers to the first three questions above, the resolution could be a little more complicated.
Regards,
B~