As you probably inferred from my post, I did nothing at the time. After the game, probably I would have said something to them, however, the trail came up to me first. He said, "We blew it, didn't we?" I said that if he was referring to that call, the answer was yes.
He then asked me if he should do something about it, like apologizing to the losing coach. I told him the best thing he could do was learn from the experience, make sure his partner knew what happened, and study the rules a little bit better.
Briefly, I then reviewed the four elements necessary for an over and back call and also what constituted the gaining of team control when none exists. That took about 60 seconds. He thanked me and promised to attend every clinic he could.
I thought he was truly sorry he blew the call, and I told him not to dwell on it and just do better next game.
Heck - even I made a mistake once
(some coaches would say it was when I decided to become an official)