I had the same thing happen. They told me that it was nothing wrong that I did, but that their client had decided not to have people assigned to do permanent checks at many of the theaters.
I've noticed since then that the theater I used to do checks at has far fewer trailer checks going on at all. I suspect they canceled the permanent checkers because they couldn't really require that someone be available every Friday when they might have a trailer check available only once a month or so.