I have trawled through the ‘ Help ‘ sheets over and over but cannot find a section that applies.
There's a link to eBay's money back guarantee in every listing, and you shold have opened an "item not as described case". eBay would have required the seller to refund you in full, and to provide a prepaid return label. eBay may in some circumstances allow sellers to reduce the amount refunded, for example if the item is returned damaged. But you should have been able to appeal this.
Did you follow this procedure - all that you say is that you "returned" it?
Your question is terribly unclear. You say that the seller gave you a partial, two-thirds refund. Then you say that he sent you a replacement, which you also returned. Was any or all of this done through eBay, as it should have been? It all sounds so chaotic that it's not clear whether eBay was even involved?
Finally, you opened an item not received case for an item which the seller could prove you had received, so it was obviously closed.
If the item not received case was the only case you opened through eBay, it's possible that they may still let you open an item not as described case. You would have to contact customer support. I hope that you have tracking evidence that the item was successfully returned to the seller, as without this it would be pointless even to try. Good luck anyway!
