A lot of mistakes here. Bad on the ref, bad on the coach.
To those that can't believe how this got missed, sign up and ref a game. For everything you see, you miss 10. Not saying you can't have a say, but you will understand how 'obvious' things are missed. As to the mechanics, the white hat in a 5 man crew is the only one who should have seen this, maybe the wing official, but he should have eyes downfield on receivers/dbs. You can see that the R was behind the quarterback and therefor probably could not see the illegal helmet contact even if he was looking for it. Also he was moving, good officials hustle to their spots and stop to watch as critical plays happen because you see more when you are stationary. Our crew talked and all 5 of us had a 15 yard penalty with no ejection after seeing the replay.