There are two places where the schedule is kept. One of them, for staff and phone goons yoinked to pretend they're staff, is a simple spreadsheet stored somewhere on the system. That's the one that the supervisory-type person changed.
(Incidentally, I am not the only phone goon yoinked to pretend we're staff who is confused as to who our direct supervisor is; Trendy Chick Super was asking about that the other night. It could be one of about half a billion people, actually.)
There is also another place -- the little system that keeps track of the phone goon and phone goon yoinked to pretend we're staff schedules and the jobs we know how to do -- the system that makes up the people/booth lists and the seating charts -- that schedule is contained. The supervisory-type person did not know about this one, and did not know that it was necessary to change things there.
So I was scheduled in last Sunday morning, but not Sunday evening. (I was check-in Sunday evening, so I got to see that I was put down as an absence on the Sunday morning shift, and note that I should not have been scheduled in, and was in fact there in the evening.) I was not scheduled in Monday. (I was check-in on Monday, and again noted this on the paperwork.) I was scheduled in on Thursday, and put down as a no-call/no-show. Snarky Lady Supervisor was very curious about this, as that's just not like me. "Um, because I wasn't scheduled in?"
Things got fixed in the system. Things got fixed in the system fast. My bad attendance points were taken away. The supervisor who'd unknowingly caused all the ruckus had the error of her ways (needing to change things in both places instead of just the one) pointed out to her. Peace and happiness ruled the workplace, and lo, all was good.