It was a headslap. They didn't show it on the second replay. I agree that it was a BS call, but he did do it. Probably made up for that pass interference they didn't call earlier in the endzone in the first half. Not the flag they picked up but the play previous to that. The defender was holding the receiver's arm down.
I still think that, on a good day, the Pats should win that game. I didn't realise that most of the team had been suffering with a viral infection, though. I guess it might teach me to research the bets a little more.