The refs were all focused on the puck. In all likelihood, probably in expectation of a shot (not to mention a player with the puck and a player defending him pass right in front of the closest ref).
It should have been called, but the refs didn't see it...sort of like those old boxing matches or the situation of the "distracted referee" that professional wrestling sometimes exaggerates to make look somewhat real (granted that involves someone actually distracting/yelling at the referee in a one on one sense, but still).