Feeling guilty?

I work in a jail. Friday a girl was having issues in her  dorm, one of my supervisors asked me to handle it, and I moved her to another dorm. Yesterday my staff sergeant came bolting in and was talking to me and another girl. She snapped, "and who moved ---?? She has an alert, so they didn't bother looking. That's ok--ill go and check and find out." This supervisor kind of acts like people don't make mistakes and talks about officers behind their backs to other officers when they do. I was about to tell her I'd been the one to move her when she stormed out, but I wanted to figure out how to word things to best explain myself.