Alright. Someone traded me, but I did not accept the trade. I opened my merchant to edit items, and suddenly I was in the trade instead of my merchant. I finished the trade and tried to open my merchant, but nothing came up. I thought CC'ing might solve the issue, but upon channel switch my merchant instantly disappeared and it was near that someone stole my spot.
I think your merchant had nothing set up yet so you lost the spot. As for clicking on stores, usually exiting and re-entering the map works for me. And also going to the cash shop.
No, I definitely had items in the merchant, since I had to visit Fredrick to get them back before being able to set it up again. It disappeared exactly the same time as I changed channel. Have you tried this out?