I had a similar situation happen to me about 6 years ago when I bought a Rebel (300D) + 3 Sigma kit lenses on eBay.
I purchased it through a 'Buy It Now' auction and was promised I'd get it in a few days. After about 10 days I contacted the seller and he told me it was returned because they could not send it to a PO Box. I gave him a physical address and within a few days it was at my doorstep.
When I received the camera. I tried it out, took 5 or 6 pictures with it and all of a sudden the images were coming up as half exposed on the screen until eventually (after the 10th or 12th picture) there was nothing but a colored line running left to right about half way down the photos.
I contacted the seller. He said send just the body back and they will send me a new one.
About 2 days later I had a parcel slip in my PO Box. I went to the main counter and handed the lady the slip and she came back with a large box (about the same size the 300D came in a couple days ago. I opened it up in the car and there staring back at me was a Rebel XT (350D) with 3 kit lenses and everything else that came with the Rebel. I thought well, maybe they sent me a whole kit by accident to replace the defective body. I went to work.
The next day (I worked the afternoon shift so I didn't get home until 10:30 at night), I received a smaller package at my house. It was a Rebel (300D). So now I'm completely baffled at this point. I called the seller and talked to a sales rep/shipping guy. I told him what had happened and he looked on his computer and said "No, we only shipped out one camera not two". I said "well, I have two right here in front of me both with your address on them. Where would you like me to send one"? To which he replied, "Nowhere. We only have one camera sent to your address on record". I said "what about my PO Box"? He said that one came back. All in all, this guy wouldn't take my word for it that they had sent me to cameras. So, I closed up the 350D and put it in my closet figuring they would eventually send me a nasty letter telling me to ship it back to them. I waited a month, 3 months, 6 months, 10 months.... Nothing came. At that point I figured, screw it. They don't want it, I'll keep it. So I had a backup kit for free.
I just love eBay screw-ups when they work in your favor!