The sellers store is gone.
Go to Advanced Search at the top right of this page.
Search for the seller's name under Sellers.
Does it show that the seller is Not A Registered User?
If so;
It is possible that this is just a glitch, like the seller forgetting to update the expiry date on the card he pays his eBay fees with.
In that case, wait about 20 days, (Don't panic!) to allow for delivery of the item.
But, more likely, the seller did something dreadful.
You can open an Item Not Received dispute through the Resolution Centre at the top of this page.
You can get the information you need by going to your Paypal account and checking your payment.
Again, don't worry. This will take a little time, but both eBay and Paypal have very strong Buyer Protection policies and your money is safe.