The first time I noticed the emerald carbuncle on the wagon, I tried to target it and realized that it wasn't target-able, that it was an NPC (more like a feature of the environment). I had seen the Miqo'te Arcanist walking around the booths in Mor Dhona, sniff and shouting for a "Ruby", to which I assumed was the name of one of her companions. It was today that I made the connection that the carbuncle's name is Ruby and she disappears when the Miqo'te appears and starts looking for her. Today I saw Ruby at one of the booths, sniffing around before disappearing as if it were dismissed.