I went to a store and my purchase wasn't in the bag. What can I do?

I went to Abercrombie & Fitch at the Eaton's Centre in Toronto and bought a few items for Christmas. I bought two sweaters, two sweatpants and a bottle of perfume. Less than a week later I decided to wrap the gifts. I wrapped the sweaters and the pants but couldn't find the perfume. I still have the receipts but I don't know how to approach the store's workers or if they will beleive me.