Back to the OP... What does the tracking info show? Does it show it was delivered? Whenever I've sold on eBay (which is rare) I've always paid for tracking for just such an occurrence.
I wonder what the rules for small claims court is - do you have to be present? You could go back to the buyer, lay it out that you believe they are scamming you, you have proof of shipment (and delivery?), they have tarnished your reputation on ebay to the point where you are refusing to sell there anymore. You are refusing to pay and they can take you to small claims court. You can provide the emails from eBay stating they always side with the buyer, and the multiple instances of claims from the buyer. I would think anyone just trying to scam you would back down when they realize going to ebay isn't going to work anymore.
I don't think I've ever had a real problem with ebay but I scrutinize every listing I consider for possible B.S. Recently I ordered an indie LP record from the 80s that was listed as sealed. I highly doubted it was an original, still sealed 25 year old record but there were pictures and the seller had an excellent record so I went for it. Right after they said it was shipped the same item was relisted! I was pissed thinking I got ripped off. It came and yes, it's exactly what they said it was. Couldn't have been happier.