Live Ball Treated as Dead Ball Foul

[GPC2]

In yesterday's scrimmage we had a play that I need clarification on. A21 broke off a very long (60+ yards) run. I was the LJ, and on the other side of the field and (apparently) well behind the play, R flagged A72 for a personal foul at A's 40-yard line - basically A72 pancake blocked a B player that had no play on the ball. The R insisted that this was a live ball foul to be administered from the spot of the foul, myself and the BJ thought that this was a live ball - treated as a dead ball foul. When I got home and read my book I didn't really get the clarification I hoped to get.

Rule 9-4-3b states that No player or nonplayer shall charge into or throw an opponent to the ground after he is obviously out of the play, or after the ball is clearly dead either in or out of bounds.

This obviously is the play that we had, and it is no doubt a personal foul - BUT where is the spot for administration? It seems to me that the R was correct....