I Just Purchased A Tiffany & Co Necklace On Ebay But It’s Completely Fake!! What Options Do I Have?

I bought the Elsa Peretti Madonna pendant and was under the assumption that it was authentic. This is the actual listing: http://cgi.ebay.com/ws/eBayISAPI.dll?Vie…
The seller never stated it was “authentic” only to “Bid with confidence” because she had 100% feedback. This is such bull. I am so mad! Is this person off the hook because they didn’t state it was Authentic? I would think that just because they were using the trademarked Elsa Peretti name,that it was implying it was authentic…. HELP!