He was absolutely robbed! Players shouldn't NEED challenges, that's what the linespeople and umpire are for. The linesperson missed the call AND Mohammed missed the call. Period.
If either one had done their job properly, the match would have been over. Now it is very likely that the kid will lose this match. A match that he ALREADY won. Very bad.
He was only a victim of that one bad call because of the 3 bad calls he made himself.