Keep in mind that reaching out and paying the seller outside of eBay risks losing your eBay account, as it violates eBay rules (eBay will miss out on their share of the payment). I ran into a similar situation not too long ago, and ended up having to live with feeling lousy about it. In your case, the seller was given ample opportunity to respond to eBay and defend what happened, and chose not to. Essentially, he chose not to be paid. That is not your fault. Please don't risk losing your eBay account over it.