If you have paid by card they can trace the payment on the back office system, i you paid cash and can tell them the exact time more or less and date, they may let you have it, it depends how you approach it, if you came into me and explained, and asked if i could check the back office system for the garment's SKU number going thru on a particular till at an approx time paid by cash, they will know you are genuine and may accept that. You need to ask them to look, it is always worth being really really nice to the staff, and above all, honest. Your big problem is the tag, if you cannot re-attach it then they can simply say no exchange, never mind refund.