The seller is responsible for his own listing, period.
If you complain to ebay they do take this sort of thing seriously, they cannot force the seller to honour the contract, especially after he has refunded, but they will issue a warning to him that he is in breech of the selling policies. If he continues to do that he will be excluded from the ebay community.
The seller has 500+ feedback, and therefore cannot argue he is a newbie and didn't understand. You should be able to still leave him negative if you wish, although that won't bring the item back to you either.
I would contact him and explain that you are going to make an official complaint as well as leaving him negative feedback as a warning to other potential customers that he may not honour the listing, give him say, 10 days to make good. You will have a further 20 days after that to instigate a complaint if you wish.
Hope this helps a bit.