TD's can't be challenged. They're all reviewed from upstairs. They can't review penalties such as if there's a hold. So I'm not sure if they could call a TD back due to a penalty.
They review the whole play as it was a TD. If they reviewed it, and it had been illegal, they can call it back. It happened in a game a few weeks ago, though I can't remember which one.
Nonetheless he should have brought that red over and talks to him. All the great coaches do it. Get in their ear a little. You can bet your ass Tomlin would have.