REMAINING ON THE FIELD OF PLAY

Question:
In a U10 Premier Boys game a defender stood in the goal behind the goal line at the far post on a corner kick. This team did this on every corner kick. On one of the corner kicks the goalie when up to catch the ball but dropped it into the field of play and a attacker kicked the ball to the post where the defender was standing behind the goal line. The ball struck the defender right at the goal line (The ball never complete crossed the goal line so no goal was scored) The referee allowed play to continue with no call.

My question is should this have not been deliberately leaving the field of play without the referee’s permission by the defender that left the field? Advice to referees on the laws of the game 3.9 say about accidentally passes over in the course of possession of or contesting for the ball. It looks to me that this team was using the tactic of standing in the goal area to have more time to react to a play.

What should have been the correct call.
Thanks

USSF answer (March 21, 2012):
Players are not supposed to leave the field of play at a restart without the permission of the referee, other than to fetch the ball and to take the kick or the throw-in. That applies to defenders as well as the restarting team. In your scenario, if any part of the player inside the goal breaks the vertical plane of the goal line, then that player is still in and on the field of play.

If the referee knows for certain that the player has left the entire field of play (confirmed by the AR), then the player should be cautioned.