http://www.youtube.com/watch?v=Pj_DfwmQG_k
I think its pretty obvious that their helmets do collide here. I can see why you're trying to make the case that they didnt touch because from the camra angle given it looks like the defenders helmet only hits the receivers shoulder, especially if you pause it at 26 seconds. But when the players both collide you can see the back part of the defenders helmet hit

