Kieron

There's a display quirk I've run into several times when I've been upgraded after I've checked in: my seat assignment will change to "see agent", and the phone waitlist will move me to the bottom of the list. The gate agent always has to call it in to release the actual seat for me, though half the time they've already done so before I reach the podium and already have a new boarding pass waiting for me. Is that the sort of scenario you saw?

I did run into a problem with that recently when checking a bag at SFO - the counter agent insisted that I was still on the waitlist but not upgraded, and wanted to reassign me to an open coach seat (in the middle, in the back). The gate agent was much better informed, straightened it out immediately, and handed me a boarding pass for 1F. However, this situation was an unusual exception... though maybe it's because I usually don't check bags!