Once you see a player go out of bounds, you should immediatly throw your hat or bean bag to the spot out of bounds. Like it was said, the spot in this case doesn't matter since it was a loose ball foul. Once you see the player come back in bounds without having been blocked out of bounds, you should throw a flag for IP and R would have the choice of accepting the IP and having K backup 15 and rekick or decline the IP and go with the illegal precedure penalty from the kick going out of bounds. The kid is going to be thoroughly confused with all those options
Not to nit pick, but there would be no PSK regardless since this was a free kick.