Is that seller by any chance listed as being "No longer a registered user"?
It's all bad news, I'm afraid. After 3 months ebay/paypal can do nothing to help you. For that matter, buyers are out of luck after 45 days. That is the deadline to file a Not Received claim. Have a look at the following link:
http://pages.ebay.ca/help/buy/item-not-received.html
If he is not a registered user, all listings associated with him are purged from the system. At this point you cannot even leave feedback, although that would be a small consolation anyway.
Your only option is if you used a credit card for your payment because depending on the card you may still have time to do a chargeback. If that is an option for you, do it now by calling the 1-800 number on the back of the card. Have all the transaction details on hand (you may need the receipts in your regular email) when you do.
In future, if you have not received an item after about 4 weeks, contact the seller. If you do not get a satisfactory response, open that claim no later than day 43, and do not close it until you have either your money back or your item. A closed claim can never be reopened.
Truly sorry. 😞