Just had same experience as OP. Lots of F seats suddenly disappeared, no upgrade list showing in iPhone app, me still in Y. Hoping for offload bug hiding actual upgrade, went to gate early and saw myself at top of cleared list. All well in the end, but nonetheless annoying.

As an amusing aside, the RCC matron apologized that it took quite awhile to offload me to get my FC boarding pass because she was now forced to use the prehistoric Shares system until Fast Shares becomes a reality next year.