The reason why AA won't do anything (like forcing award inventory open) is because in their system the pax still has a valid reservation, just no seat assignment. However we all suspect the flight is overbooked in the F cabin. "New" OP should ask point blank whether this is the case - I believe its AA policy (if not DOT) to answer truthfully. That may shed some light, but doesn't really help much. I think that unfortunately the best new OP can do is monitor alternative routings for availability. S/he can also set an EF alert for F on this particular flight. So if another pax cancels, he can try to get the seat assignment back asap.

But in reality, AA doesn't need to accommodate over bookings until they become oversales, which unfortunately doesn't happen until more than 8 pax check in, at which point alternatives are probably very limited.