If a store turns you away, ask for a clear explanation. Sometimes, it's just a matter of misunderstanding, and a little communication goes a long way.
Often, there is a time limit based on the store's policy, so it's a good idea to act quickly before the sun sets on your chances.
Missing Receipt Declaration is a document you fill out when you've misplaced a receipt and need to declare it as lost in order to get a refund or exchange.