I've returned things many times....sometimes just a couple of minutes after I purchsed it. I explain the item was a present from someone, and I just received a text from [husband, son, friend, sister-in-law] that they'd already bought the item. If the explanation is accompanied by the right amount of exasperation and eye rolling you'll get the salesperson to really comiserate with you.
Happiness is not a goal; it is a by-product. Eleanor Roosevelt