What nmars has said is correct. Once the seller takes the money out, and you file a buyer's claim of non-receipt, you will get no money back from PayPal. You just lost your money.
There's another option. If the seller has already withdrawn the funds from their PayPal account, and if you used Paypal, using a credit card option as payment, you can still contact your credit company of non-receipt of goods. The credit card company will then do a 'chargeback' against PayPal, and PayPal is out of the money.
If you used existing funds in your PayPal Account, or bank account option, you are out of luck if the seller withdrew all the money.