It may show up again, just check after GMT midnight every day. I think POUGs do clear down after AUPs but yes they can come and go, and probably more than is evident from the App since it's possible for the App to show a POUG which is no longer available, the update for this on the App is not real time.

The one slight risk here is that normally a clean AUP won't interfere with the ticketing, but for POUGs you need your reservation to stay in the self-service channel, otherwise it won't show up. If they had to struggle with the AUP process it's not totally unknown for the ticket to end up being manual, due to too much data falling off the reservation. From what I can make out OTA and corporate bookings are particularly at risk here. So realistically there is a snooze/lose risk here.

UKtravelbear is right that you can't look at the seat map or the selling classes of CW to get a view of the flight loading. The most important clue is the selling classes in WT!