Illegal Fowrad Pass or Not?

[Dyker Ref]

THE PLAY

QB takes the snap. Runing Back(RB) runs **IN FRONT** of him and the QB hands it off to the RB who, again , is infront of him. Th RB than drops back an throws a completed pass.

QUESTION:

Is this a legal foward pass by the Running Back. He was behind the line of scrimmage, but I consider the hand off to the first and only foward pass since th QB handed it off to the RB who was directly in front of him.

My inital call was illegal foward pass, but I was overruld by a league offical.
WHAT'S THE CORRECT CALL?