If it was a WWF quality body slam, then no I would guess it could not be missed. However if everyone is running/jumping around on a corner kick, and I am sure both sides were shoving and tugging alot cause everyone does on corners, and a player who jumped up was grabbed and push by another player in the crowd well... Refs are trying to watch alot of things during these kicks and a lot of fouls get missed.
Perspective here is key to remember those in the stands have a great crowd view from some what 3/4 above, the ref is level with looking thru crowd, while sideline is watching goal line thru a moving cluster. Oh and you tend to see your players being hit/fouled by them it is human nature.
