Originally Posted by
hw711
I think he used miles to do the upgrade so it should be confirmed.
Right, I should have rephrased that to be "When did you show up? If within 15 of the departure time the seat was lost."
IIRC regardless of the seat if not within 15 of departure you lose your confirmed seat and the GA probably gave it away to another PAX. As such, the paying PAX now has a choice take the flight and whatever seat is available or wait for the next flight with same class of service. If the former, then they should get their miles back (or if paid a refund).