I think it is HIGHLY likely that with only 29 seconds there is no way they would have gotten in field goal range.

There would have been a lot more pressure on them and they would have known how little time they had. Also, defensively, it is a lot easier to play just to run off 29 seconds than to have to defend when you know the other team has PLENTY of time to get in field goal range.

Furthermore, I think you can definitely conclude that there would indeed have only been 29 seconds on the clock at the end. On the Steelers final drive, they were doing everything they could to eat clock. They were definitely draining it all they could, and certainly would have done the same if the clock had been correct.

I think without this error, it is about 80% likely that the game would have gone to over time. That doesn't mean the Steelers would have won by any means. I'd actually give favorable odds to the Pats in that situation.