That is a good question. I didn't see if a ticket was reissued when we were moved to J, so I don't have that as leverage (only have pics of the seat map showing us in J). However, the EXP desk supervisor talked to a seat desk agent and confirmed that we had been upgraded last Sunday, then downgraded this morning.
Also worth noting that I had an Expertflyer alert set for C inventory (applied SWUs on 1/31/23) in case some became available, then I would call and ask. However, I still have not been alerted to any C inventory coming available on the flight.
Supervisor sent a note up the chain to try to find someone to reinstate the upgrades, but it will likely be until Monday to see if we get moved back.