You can sue the store (including potentially in small claims court, where you could act as your own attorney, saving on legal fees) to recover your money. A store or vendor is not allowed to keep your money without giving you the item you are purchasing; if they legitimately ran out of stock and simply could not furnish this item, they have to return your payments. They have, most charitably, breached the agreement between you and them by not furnishing the item they agreed  to and for which you paid; less charitably, they are committing a form of theft.