something similar happened to us last month. confirmed upgrade for wife and i, and suddenly we noticed while waiting in the lounge for our flight that we were suddenly waitlisted. No one could help (airport customer service, phone customer service, lounge customer service) because it was too close to departure, had to wait for gate agent to show up. explained the situation to her and she seemed unable to do anything. i told her this was unacceptable, she asked if i wanted to talk to her supervisor(?). After waiting a while as boarding was getting ready to start i reapproached the agent as i had not spoken to anyone else yet. She told me to standby that the supervisor was fixing it. I watched them downgrade two people who attempted to board in first class. We finally were able to board about midway through the process.

What i don't understand (other than why it happened at all) is what happened to our seats. We got one of our original seats back, in the other seat was a 100k million miler who said he had that seat for a while. He offered to switch seats so my wife and i could sit together. When i explained to the flight attendant why the names did not match her current list she said she saw our names in our original seats on her list while she was on her previous flight. She also said there was no way that million miler would ever be downgraded (HVC?).

So when we lost our original seats at about t-2 hours why where the replacement people not the ones that were bumped? it almost seems there were multiple people assigned the same seats at the same time?