Arrived at the location on the map of an Antiquarian Ascended realm Essence Trader and found the wagon at the map marker but no trader. Looked at the map again and the marker was gone. I can not purchase the Astrolabe Ascended card and progress as a result.
I tried logging out and back in. The icon appeared on the map again and then vanished when I approached.
I then tried logging out/in with the area in slight and, as I logged in, saw the name of the trader fall through the floor.