Hey there @jaguarssoul! I'm not completely sure what you mean by taken away? If someone buys an item from your usershop, it will be removed and transferred to the buyer, if that's what you mean. And with certain items, you can set your shop to only sell one at a time, by checking the box that says "sell single units" before you place it on your usershop.

To answer your other questions, yes, if someone buys something from your usershop or your auctions, it's possible for them to send it back to you via the "create personal trade" feature in their item inventory. They can also set a price for it, allowing you to refund them.

@jaguarssoul In the game tab, click on Items > Usershop. It'll bring up a list of your current items that are stocked in the user shop. You can change price and remove items from that menu.