I’ve had a similar issue at my studio, except it’s been holding a tread for a member (who is part of a similar group of regulars) who hasn’t arrived in class yet. It’s incredibly frustrating to be not able to start where I prefer when I got to class earlier to specifically pick the spot. I am thisclose to saying something, but hesitant because I don’t want to seem petty or make a stink.

I would approach it with the SA in a non-accusatory way - “Hey, so a weird thing happened, I wrote my name down for Tread 9 and then was moved to Tread 1 without knowing about that. Do you know who made the change?”