Hilton Honors has been auditing accounts with a new computer system/program and removing promotion codes and the associated points & benefits that came with those promotions if you were not supposed to be targeted for the promotions.
This is my guess what happened. I had a fast track to gold promo on my account and then one stay before I would have hit it the hard way the gold was taken away. I was told I wasn't eligible for the offer I signed up for. It seems the agent entered the wrong promo but it didn't matter since I was given back gold the next day or so after my stay posted.