Yep! By selling bitcoins on their website, technically you are in violation of their TOS.  It's like telling a judge that a dug dealer ripped you off.  The judge isn't going to side with the dealer, but he 's going to dismiss your case since you were doing something that you shouldn't be doing anyways.  Same here.  Paypal and ebay don't care about your proof.  You are doing something against their TOS so they don't care about your case.  I wouldn't be surprised though if the other guy also got a warning not to make those kinds of purchases in the future.