July 2, 8:25am- I think I know what's happening, but I send payment even without the invoice, as I'm confident that there's little financial risk
July 2, 10:46am - Payment refunded (*see below)
July 2, 10:48am - Unpaid item case opened by seller
July 2, 12:48pm - I respond to case, indicating that I will pay
July 2, 12:51pm - Case closed by seller, giving me no chance to fully respond
July 2, 1:10pm - I appeal the unpaid item case/strike, and it is immediately reversed

I'm not 100% sure but at the point when the seller opened a unpaid item case, you should have resubmitted payment and then clicked that payment has been sent. This would have made him close the case and turn the tables where you could open a case against him if the product does not arrive. Once the case is opened, he would be forced to send the item (with tracking) or deal with his own strike.

The damage to this guy's star ratings is pretty bad...enough to give the lie to his overall feedback percentage.

If you scroll down his feedback far enough you start to hit mutually withdrawn feedback...which is a klaxon going off when I look at a seller's feedback.

Also, this guy has a history of nasty responses to negative feedback.

Instead of "Sorry you were dissatisfied - please contact us"  this guy snaps back at his customers.

IF I give anything less than all five stars to a seller I give all one star ratings.  Thing is, in RPG purchases I seldom to never encounter a dishonest seller.  Everyone is usually really nice and quite reliable.  

Electronics strikes me as a category destined to be dotted with scam artists...like that link to the Judge Judy case on the Acaeum a while back.  The thief had hidden the words "picture only" in her listing and felt justified in ripping off customers.

You were wise not to send this individual any money.  Hit him with negatives, and move on.