Did you ever think about what might have happened from the sellers viewpoint?
I went to look at your EBAY transaction with this person and he has had 1380 positive feedback scores, with only 2 negative feedbacks. This kinda tells me that he is most likely a very professional seller.
Owning a small business myself I'll bet UPS told him everything was OK and it would be there by Wednesday, and most of the time UPS is very reliable, but this time it wasn't (It's happened to me). So chances are he took another radiator out of his stock and shipped it to you, hoping to straighten out the UPS thing on his first radiator later.
As far as him not responding to emails I don't know what the deal was with him, but I once purchased something on EBAY from a company like you did and I tried to contact the seller for 2 weeks about it with no responce, so finally after I got completely pissed off about it and got his contact information and called; the guy was in an ATV accident and not expected to live. No one else in his small company knew how to run the EBAY thing, either. But he did recover and called me back about a week later (from his hospital bed) and apologized and said he would get it to me ASAP. (His company sent it Next Day Air)
Usually on a thing like you experienced I would just not leave any feedback at all, rather than leave negative unless it's a clear that the guy was out to screw me.
That guy might have tried his hardest to straighten this out, but you left him negative feedback anyway. (I would have probably done the same thing by leaving you negative feedback in responce)
Pat
www.nitrostreet.com