Flew IAH-east coast recently and didn't check the upgrade list until the morning of departure for a 6:30pm flight. I was #1 as a 1K on an S fare. I presume I was #1 the whole way as the flight was sold out up front for days.
Two hours before departure a seat opens up front and I was also leapfrogged by someone on the list. I wasn't totally surprised as all the flights earlier in the day were also zeroed out and I assumed someone got booked into the last Y seat on my flight in the afternoon.
Fast forward and as I'm being driven to the airport I get a notification that my seat has changed to the F seat that was showing unoccupied. Person who was #1 on the list remained there. Later I realized that the person who was #1 on the upgrade list was also #1 on the standby list.
I'm assuming this was a displaced F passenger? Maybe a GS who missed their flight? Not sure why I would jump him (yes, it was a him as I saw them go up to the podium when they were paged as they cleared into an E- seat).
-RM