A shop type which is one of those magical shops that you only see once and isn’t there when you go back, in which you can buy only one item. One possible implementation is that after buying an item, you are teleported out of the shop or even levelported to a nearby level, and then the shopkeeper and the rest of the items in the shop are removed, as well as possibly the entire room. There may be some need to prevent normal methods of theft from the shop. Alternatively, you could be permitted to buy multiple items, but the shop disappears after you leave.