Bench player picks up live ball

The umpire was enforcing it like it was thrown out of play. When it is the offensive team that does this you can't do that, otherwise you would have teammates running out of the dugout regularly. There is an adage in baseball that says punish the team that screwed up, in this case the offense. I would kill the ball, leave the runner where he was and admonish the kid not to do it again. It didn't cause a problem or negate an chance for an out, so there is no need to do anything more. If it had been the defense, then I would have awarded the runner third.

I concur, similar play would be say a play at 1st, say a PO attempt of R1 that gets by F3 and base coach picks it up and hands it back to F3. No harm no foul, but, yes, it should be squelched straight away. Because, what if R1 and R3, PO attempt of R1 gets away, R3 breaks for the plate, now BC picking it up, we have a problem. So yes discourage any touching of live ball by Offense and their teammates.