What can you do? Well, if you used a credit card you can try for a chargeback by calling the 1-800 number on the back of the card. If this is a possibility for you, do it now as there are deadlines for that, and have all the transaction details (electronic receipts, the postal receipt when you mailed it, dates, confirmation numbers, the works) in front of you when you call.
Otherwise it is too late now for ebay or paypal to do anything. Did you open a claim officially, or were you just hoping the seller would do the right thing? You see, you have only 45 days from when you paid to file a claim for 'Not as Described'. Ideally you should file no later than day 43.
I sure hope it wasn't expensive. Did you by any chance ship it back with Delivery Confirmation? Or did you use cheap-o mail instead? When you return an item you need a Delivery Confirmation number to show the seller received it back. Otherwise the seller can say "Return? What return?"
Have a look at the following link about what to do if there is a problem. It is the most important information you will find if you plan to use ebay much:
http://pages.ebay.ca/help/buy/item-not-received.html
Your seller has a feedback of over 7000. This is someone who knows the system. He knows now that there is nothing you can do, and you have no item and no money. If you can do a credit card chargeback, great, - otherwise, you've learned an expensive lesson.
On the bright side you left him a well-deserved negative, you can add one last response to that neg if you want to, - go to your feedback page and scroll down to where it says Follow up to feedback left. There is no time limit for this, so if you have one last thing you would like to add, give it a bit of thought before posting.
