Balk With No One On?

[DFM7]

During ground rules in a game last night a coach told my partner and I that a umpire in a previous game had called a balk on his pitcher with no one on. The umpire then added a ball to the count of the batter. I felt this should be no call but my partner agreed with the call. I thought that I had read, in this forum, that this should be a no call under OBR. I have gone through the last 45 days of topics but cannot find that thread. Can someone verify the call wether right on wrong and cite a rule or case.

Thanks.