Non-MLP auction from eBay with missing items - What now?

[Prideth]

I'm kicking myself over this transaction as it felt a little weird to begin with, but I didn't follow my initial instinct. Now I'm not really sure what to do as I've never been in this situation before and wanted to see if anyone else has experience with this.  Here are the facts of what's happened:

• I was the highest bidder for an auction that ended without meeting the seller's reserve.
• eBay allows the seller to offer a "second chance" to the highest bidder of an auction that didn't meet reserve.  The seller contacted me and offered to sell at a higher amount, which I negotiated down, and we agreed on a price. 
• The seller didn't seem to know how to re-list the item at the negotiated price so that only I could buy it, so I (dumbly?) told them they could send me an invoice via paypal with a description of the item and I would pay that way.  I really wasn't sure how to handle this either, but that seemed like a decent way to cover my butt.  It still felt a little weird but I wanted the item, so that probably swayed me.
• I requested tracking and the seller complied;  I get the item(s) as expected, but, alas, there is a critical piece missing!  I contacted the seller (all of our correspondence was made through ebay) and let him know - he is adamant that the piece is in the box.  It's definitely not.

How do I go forward from here?  I'm positive I don't have the missing piece and he is also adamant he doesn't have the missing piece.  Since we kind of settled 'outside' of ebay... what should I do here?  Has anyone else had an issue like this?  I regret doing it that way (now) as I'm pretty sure I'm not covered through eBay protection, but it hurts to think I'll be eating the cost.  (I suppose it would be a hard lesson learned.)

Any advice?

[bluerose9978]

Maybe call PayPal and see if there's anything you can do? I called them recently with a problem seller and they were very helpful! That is my best advice!

[banditpony]

I believe you still have buyer protection from Paypal. I think you can open up a dispute through paypal... Just as long as it wasn't a personal payment.

[Ringlets]

That's a bit of a toughie situation and a no no as regards going through ebay since you completed the transaction away from there - but as the others said you should still be able to do something through Paypal. Giving them a call might be a good option too