I would like some feedback on a situation.

I recently ordered a jib sail from a well-known company. When I got it I quickly realized it wasn't a jib, but a main sail! I only paid for a jib, but got a plain white main sail. After much deliberation and thought, I finally called the company and explained what had happened(they had no idea). They were appreciative and are rectifying the situation. So, fedex picked up the sail and they are shipping a jib.

What would you have done? I thought of keeping it for a back up, selling it on ebay for a profit, but I really needed a jib and didn't want to fork over more $ to get one if I kept the sail. Obviously I saved the company some money by returning the sail and I think they will give me something free for my good nature, but I don't know what yet. What would you guys have done?