I came to the conclusion over a year ago that Disney was doing something with these rooms as well. I was in the same situation of waiting until 8am to book seeing that my entire week was available. 8am hit and I refreshed and attempted to book but the booking software on Disney's end had an unexpected issue. I immediately called in to try and acquire the elusive room, refreshed my browser again and the single day at the start of my trip was gone. When members services picked up I was informed that they too were unable to book any rooms due to an issue with the software that Disney IT was investigating. So how was it that the single day managed to disappear if the booking system was currently down for both members using the site and cast members using the internal booking system? I never did manage to get the answer to that one.