There were only 6 seconds on the clock when the ball was snapped, if the bad snap-control-stand up-spike takes more than 1 second (plus whatever fraction of a second was there that the NFL doesn't show... I love that BTW) then the 5 second count off ends the game. But don't quote me, I'm not sure the 5 second count off is still there.
I think the missed delay of game penalty was the result of two things: 1 - the Browns had been called for it a lot already, I think even the refs were having a hard time believing these guys were so bad at counting to 45; 2 - "all star" refing squads, the NFL assembles reffing squads for the playoffs from "the best" in the league during the regular season (where they work as a unit, same 8 guys for 17 weeks) you see a lot of confusion as refs are used to guy X looking for "that" but guy X isn't there. I'd bet none of the 8 zebras on the field in Pittsburgh were the designated clock watcher for their group. The Steelers did a good job of pointing it out most of the time though ;)
The moment the holder, Allen, yelled, "FAHR!"
(in my best former H.S. coach voice), the game was over unless the holder could have navigated his way by foot to the endzone or, oddly enough, placed a perfectly executed dropkick between the uprights.
The offensive line started down field eliminating any chance of a forward pass which would result in an illegal man down field, offensive penalty, 10 second runoff on the clock, game over.
Any defensive penalty would have been offset by the illegal man down field, play dead, no time left on the clock, game over.
There was six seconds left on the clock at the snap. A muffed snap and a sprint to the sidelines would have taken too long and falling on the ball and calling timeout would have defintely put the kick out of Bryant's range. But then again, they could have had Shockey kick the fieldgoal right Mr. Collinsworth?