Help with a play

[AZ Line Judge]

Had an interesting play occur in a "Semi-pro" game I worked yesterday. They use mainly NFHS rules with a few alterations which wouldn't affect this play. We had two different Varsity White Hats that disagreed on the results of this play.

A's ball 2 and Goal on B's 8 yard line. A1 hands off to A2 who fumbles at the 3 yard line. The ball goes into the endzone and comes to a rest about 9 yards deep in the endzone. Player B1 picks up the ball, hesitates for a second and then steps across the endline.

What is the ruling, touchback or safety?

I look forward to the discussion on this!

Chad