Even if you pick it up later because you decide that the WR pulled down the DB (which is ridiculous) there was enough contact so that both players went to the ground, then the ball plunks the WR on the helmet.
I think this crew cheated in this game and I think they cheated in the WI/ASU game. Given the long history of PAC officials screwing teams not from the PAC and the PACs reluctance to allow non PAC officials to do their games it is not hard to believe there is some malfeasance involved.