Gwinnett Federal Credit Union cost me $500

I applied for an auto loan with Gwinnett Fed Credit Union, 780 Credit Score, over 1Mill in income over the last 2 years. They approved my loan and told me that I needed to have the Dealer send the Buyers Order to complete the sale. I had to pay $500 deposit to take the car off the market and since I had already been approved, I saw no problem doing that. When the dealer sent the Buyers Orders for the car directly to the Credit Union, the credit manager would not do the loan because "she" didn't like the idea of buying a car off EBay or Online. She found a coupe of complaints on a site like this one and she said she was uncomfortable doing business with the dealer. Never once did they condition approval on doing business with a Dealer that they approve. I had the Dealer call the underwriter to assure her that they were a legit business, EBay Power Seller with 100% Satisfaction Rating by Ebay, they still would not do the loan. I lost me $500 deposit. They should pay me back but they refused to do anything.