Wondering if it's because you cannot review penalties.
Ruled a fumble so the penalty never occurred. Instant replay can't review penalties (aside from 12 men) so they cannot change it now.
Be no different than coming back from the booth and dropping a flag for a holding call that went uncalled when the play was live.
No, they actually came out and called a penalty as a result of a review twice in one game a few weeks ago. I can't for the life of me remember which game or what the calls were. Actually, I think it was illegal touching. A receiver went out of bounds, came back in and caught the ball. It wasn't called on the field, but they reviewed whether or not it was a catch, saw that the receiver went out of bounds and then came back on the field and dropped a flag.