Following up, they were sold out at the BC this evening. I believe there is a lot of demand, and Disney has to find out how many mugs needs to be dispatched at each location.
If you're checking out in the next few days, do not despair if you can't find them! Don't hesitate to ask a CM, they might help you find out which resorts have them. Don't forget, mugs are valid in all the resorts, regarding the one you're staying at (or not staying at, if you're off-site).