My husband was really determined to find this mask display so we returned to the second place we'd tried and asked again, and there they were. I don't know if we didn't ask the right questions the first time, but it all worked out. These weren't really on display and might have been stored there while the awards ceremony was going on. Either way, they let us into the rooms they were in. There were a lot more than this!
In the last photo, you can see the sign for the museum has Santiago fighting a Tastoan.