Second comment -- the dead ball shenanigans shouldn't be ignored. A player of K initiated contact with the helmet-less runner. This isn't Illegal Participation, but it IS Illegal Personal Contact (9-4-3i .. could be slightly off on the rule, my closest rule book at the moment is a few years old, but I don't think that's changed). That is a severe safety issue and shouldn't be waived off.
One could argue the helmet-less runner also committed a foul by continuing to run down the field, but that would be delay of game. I don't think you can charge him with IP, since the ball became dead once his helmet came off. If you wanted to erroneously call it IP, then the dead ball yardage cancels out and you just enforce the facemask from the 50, but we're kind of inventing rules at this point.