While this completely stinks, I don't know if there is anything that can be done about it. I think the best thing to do would be to call eBay and ask what your options are. I had this happen to me once and I had to pay $14! I did not pursue eBay for it though because it was not really the seller's fault entirely.
On a side note, if you had recently filed a change of address, and the seller shipped to your previous address because it was what was provided to them through eBay, the post office will charge you for the forward on certain shipping methods.