I sold a set of Kyosho shocks on Ebay recently and forgot to list there was a couple small parts missing. Buyer was unhappy so I offered a refund AND return postage. NO WAY ON EARTH was I going to refund before getting them sent back though.
That's how it works in the real world and RC is still semi close to reality most times.
Can't buy something from Amain, not be happy and get your money back before returning it!
Just get delivery confirmation so you can prove it was returned and if he doesn't refund you Paypal will side with you. May wanna open a claim before shipping though. Just saved my butt doing that.
Good luck!