Did you verify that his account was BANK FUNDED, if not they can just report it to their visa/mastercard/(other major credit card.) and have the payment chargedback or stopped before you even see it.
Also depending on how he did it, he could have easily signed on through a proxy/other computer and then called paypal distraught saying he saw a charge on his paypal which he did not make at which point paypal immediately puts a hold on the funds.
Generally you're shit out of luck at this point, you would need an email from him stating he received the account etc. And a ton of other proofs before you could stop the chargeback/recovery. I lost 1800USD to this.