Looks like a definite GA fail.

There could well have been several misconnects, but you should have been brought forward before the door closed.

Once the door closed, the FAs can't do anything, so they can't move you forward even if they recognise you during the drinks service.

I agree with the above advice — write in and let UA know this happened. They should make a service recovery gesture, but at the least they ought to remind this GA to take care of the upgrades before closing the flight. I'd have thought the new no-blame system would help ward against this happening.