There WAS contact -- maybe not very much, but it was there. I think you're reading too much into the rule, Mike. This isn't basketball where contact is required for a PF. The spirit and intent of the football rules is to eliminate this from the game and you don't let a player who did it off the hook because the offensive player ducked his head at the last minute.
There are many "dangerous" fouls that we don't require injury or actual danger to occur prior to throwing the flag. Same idea here.
Joe S: I think where Mike is coming from is if you KNOW there was no contact because the player ducked his head. I don't believe we can call a PF in this situation - otherwise that opens up a big can of worms. Suppose a defender comes in very, very late intending to punish the runner who is already on the ground but at the last second the runner rolls away so the defender misses? Or the blocker during a kick play dives head first right at the opponent's knees when his isn't looking intending to take him out, but misses? And so forth.
Of course we would talk to the player as he essentially lucked out, but did not actually foul.