Whenever you shop online you have to check out the site and not just its return policy. While customer reviews are important you never know who those reviews have been written by. And always use a credit card or PayPal so that if you do get ripped off you can get your money back.
But now that the sale has been made, assuming your purchase was made with a credit card or via PayPal, contact either the credit card company or PayPal and explain the situation. They should be able to credit you the amount.