Thanks for all of the advice so far. I called eBay customer support tonight and was told "All bids made in the Real Estate and eBay Motors vehicles categories are considered non-binding." So I guess the lesson learned here is that there is no reason to pay the extra fee for a reserve since you don't have to sell your car at the end of the auction if you don't feel like it.
The dealer is a small private dealer (not a chain) that has been in business for I believe at least 10 years selling exotic cars in houston. From the research I did prior to bidding on the car they seem to have a good reputation with members on some of the forums vouching for them over the years. I spoke to the owner when I called, to no avail.
What's even more of a bummer is that my 328i got nailed with hail a couple weeks ago and is probably going to be in the body shop for a month or so (I will not be cutting any corners and am taking it to the best body shop in DFW). I don't have rental reimbursement (seemed like a good idea when my other two cars were running) and this would of been a perfect time to buy a new car rather than waste a ton of money on a rental car.
I'm going to contact the dealer again and see if we can come to a more amiable solution. I'll keep everyone updated.