I started noticing items missing as transmog options. The item itself isn't missing but the appearance options (to put on items) are. At first I couldn't find merchant's pants. Thought it was a weird decision by dev. Then after I upgraded Wayland's armor set, I tried to set to lower appearance, couldn't find them in transmog at all.
Now they are just disappearing in front of me: I changed Dublin's champion armor to its lower appearance, when I opened transmog again, there's no Dublin's champion armor at all for appearance options.
This is happening in both Raventhorpe and Dublin.