I must say I've had very good experiences buying from eBay but have never sold anything on there so I have that yet to come.
I've bought many lenses and the odd camera and with the exception of two lenses which I returned, one due to excess dust in the lens and the other with fungus, I've had no problens.
In fact both sellers were very apologetic and seemed genuinely unaware of the faults and I received a bank transfer on each occasion the same day they received the lenses back so I really couldn't leave them bad feedback as they behaved perfectly.
I feel for the OP and just hope that the crook who purchased his lens, gets what's coming to him - my only advice to selling such items on eBay would be to restrict any potential buyers to the UK and then there is some comeback with the aid of the police if they try that one on with sellers!
Ripped off for £160 once selling a lens, never got lens back. My dealings with Ebay over it were totally unsatisfactory, to such an extent I feel they were complicit in this theft. never dealt with them or Paypal again, nor will I.
We had a similar issue with a petrol toy car we sent, The prick biscuit, as he shall be named, claimed he never received it... Paypal gave him his money back & low and behold Post Office said he was known for doing it!
Baffles me that these buttmunchers get away with your stuff and hard earned money.