I had a trip where this happened. There were something like 3 seats open and I was #3. I waited to be last to board and innocently asked the GA if my upgrade had cleared (knowing full and well it had not). This prompted the GA to type a few things in the computer and clear the upgrade. If the GA told me it didn’t clear, I was going to ask why.
I felt bad for the couple that were #1 and #2 who missed this one.