I sold an item by mistake. Can I get it back?

Yes — always, and always for free. Right after selling, tap Undo on the "Sold" message (it shows for 5 seconds). Missed the undo? Your last-sold item waits in the buyback slot next to the sell chip. Buying it back costs exactly the coins you received — you never lose anything. The buyback slot holds your most recent sale until your next one, and it survives closing the app.