if they do not pass, a refund form appears on the exchange page, where you need to specify the address to which you want your BTC returned and click the "submit" button. After this, your bitcoins will be returned instantly from the same unique funding address to which you made the payment for the exchange request.
Suggestion;
1. How about a field where a refund address is entered way before an order is made. Perhaps on that page where the receiving address is entered?
I am thinking this could be convenient just in case a user accidentally closes the order page and does not remember the order ID.