Not to be nit-picky but it was 20 yards to the nearest Viking, 15 yards to the nearest play who was a Cowboy. But let's say Austin is able to return this down the left sideline. There are lots of blockers in front of him. I'd say he has a better than even chance to get at least to the 20 yard line. Can we assume there would be no holding of block in the back calls? The Cowboys have burned a lot of good returns with penalties like that. But lets assume they manage to stay clean. How much time would be left on the clock? Maybe 12 seconds at most? Probably 10. They would have two tries to get the ball into the end zone, assuming Moore didn't try to hand it off to Zeke! I like the Cowboys chances from the 20 with 2 plays a lot better than their own 45 with 3 plays, but its still a really, really long shot. So much could go wrong. A sack could end the game for example.
The coaches lying about what they told Austin is really bad and threatens to blow up the locker room. But the game was lost on the last Cowboys drive. Its that simple.