You were paid .
You shipped.
No problem.
If the customer complains in future, you may be dealing with a Paypal or credit card dispute, so I hope you have a tracking number.
Most of those disputes are solved by showing Proof of Delivery.
With PP, a Not As Described dispute allows you to demand the return of the disputed purchase before shipping, even if you have a No Returns policy.
And PP wants the buyer to pay for return shipping, which discourages all but the most unhappy buyers.
