On plays like these, we're trained as wings that if we don't see the ball, to crash until (a) we do see the ball, or (b) we get a sign from the umpire. On this play, the wings can see the supposed runner is on his feet in the end zone. Even with no hints from the umpire, all I need here is to see that the original runner still has the ball - no matter where he is now - and I'll signal the TD. The result is often a late signal, but it works.