http://resolutioncenter.ebay.ca/
Go here and open an Item Not Received dispute.
The first thing you will be told to do is to contact the seller.
If you have done that, go on to the next step.
If the seller cannot prove delivery, and does not refund you, Paypal/eBay will and go after him for their money. There will be other fallout for the seller.
However.
Is the Global Shipping Program involved in this?
Go to the same link.
Again the GSP will be required to prove delivery or you will be refunded.
Do you have the name of the actual delivery company? Do you have the address they delivered too? These may be useful in your Claim.
Don't argue semantics. That's a delaying tactic. What you want is the item or the money.
Paypal does not require a Signature for items valued under $750 (including shipping).