I need some help

So I got pretty screwed by eBay this week. In November I sold a MB 149 (I actually had it listed on here) to someone on eBay. He didn't want to pay for the insured shipping and asked specifically for USPS standard international. I thought nothing of it, however just this past week I got a notice from eBay saying that the buyer filed a claim because the pen never arrived. I reached out to him and said that's unfortunate, however I can't do anything about it. He got pissed and threw a fit and somehow managed to convince eBay to give him a refund and then they took the liberty to debit my paypal for $419...

So my question is, does anyone have any suggestions on how I can get my money back? Sellers are not responsible for items lost in shipping, so how could they just take my money like that? Ive filed 3 appeals at this point and all have been denied because they say I uploaded the tracking information too late (which is bogus). To make things even more annoying, eBay doesnt have a customer contact phone number, you have to request them to call you and you get some shmuck on the phone. I cant even ask to speak to a supervisor.

Any help would be greatly appreciated.