Fumbles

Question
This weekend my son played in a game where he was playing defense and he tackled an offensive player who fumbled the ball on the 3 yard line and the ball bounced into the  end zone he ws defending. The ball was picked up by another offensive player in the end zone and ruled a touch down. I thought the ball would be called a touchback since the offensive player fumbled before reaching the goal line. I thought this would have resulted in a change of possession then ball placed on the 20 yard line going the other way. Is this correct? In addition, what are the rules for inadvertent whistle blows by the refs once the plays crosses the line of scrimmage? We play by NFHS rules.  

Answer
Ty,
Thanks for your question and thanks for clearing it up for me.

First the ruling is correct it is a TD.
Second, there was never a change of team possession.  Team A (offense) snapped the ball, ran with it, fumbled it (a fumble is a loose ball not in "player possession" but considered to still be in Team possession of the fumbling team [Team A], it was recovered by another TEAM A player behind the defense/opponent's goal line.  Therefore the ball is dead in a team A player's possession behind its opponents goal line. TOUCHDOWN.  If the defensive team would have recovered the ball [this would be a change of possession ]it would have been a Touchback because it became dead in their own endzone in their (Team B's)possession.

With respect to an IW (inadvertent whistle)I assume you are describing a run play. The ball becomes dead at the spot when the IW occurred or they may replay the down but no time will be added to the clock.