I have a similar situation. I paid up to use an SWU SEA-JFK. They substituted a domestic F with domestic F service and upgraded all medallions as if it were a regular domestic F flight.
I asked for the difference of the fare I paid and the cheapest coach fare, as well as my SWU back since I would not have needed it. I was tossed 7.5k as a pittance. I plan to escalate and hope to have the same success as the OP.