Instant replay of Brunell the crossing line of scrimmage

[htownskinfan]

Has anybody heard any of the sports shows or announcers talking about this call? Probably not because it didn't affect the outcome of the game, but what if Brunell had thrown a touchdown on the play?

I didn't know that penalties could be called on instant replay (which is exactly what happened). There was no flag thrown on the field. So how is that reviewable? Am I missing something?