the bug still exists! but now it is activated when you change internet connection( in my case i use the phone internet and the home internet). in the video can see i still have the transmog in other items but cant apply to new ones
https://youtu.be/mqjt4vy6urY
Mine also disappeared just a bit ago. Was trying to decide what to wear for the Running of the Trolls on Feathermoon. Finally decided on a look and after a much longer than usual log in, my Sprite Darter and Wooly Wendigo sets went missing. They were there this morning. 