All sales completed in Trove should be considered “as-is”, final sales, with no returns or refunds. This is why it’s very important for you to check the items you’re buying thoroughly. When paying via debit/credit, you should only press Complete to move funds to the seller after you’ve inspected the item completely and made sure you’re fully satisfied with the item you’re buying. Similarly, if paying in cash, don't hand over cash until you're absolutely certain you like the item you're buying.
If you need to contact the seller once a transaction is completed, you can do so by finding the purchased item on the Offers Screen, tapping that treasure and then tapping the Message Seller icon on the top right of the listing screen.