Ebay auction

I won the above item on 5/17/07. Sent cashier's check for $5,720.00 to address sent to me by ebay after I won the item. Ebay did not say not to send a cahier's check. You usually have a few days maybe up to 2 weeks at most to pay for an item. I paid for the item around June 4th. Way down on June 14th they notified me that someone broke into their website and set up a false auction with the official ebay logo. They are refusing to accept responsibility for the lack of security at their website. They have so far refused to return my $5,720.00. The issue is the lack of security, not whether I used paypal or not.