Hello 'macstampdouglas',
Since things do not appear by magic, I'd suggest changing your password right away. From your My eBay page, select the Account tab, then from the left pick Personal Information. Under where it says Account Information, find Password, and use the Edit on the far right. Then do not tell anyone alive what it is, or even that you've changed it.
As for the interloping item, if you cannot get anyone in your orbit to confess to the purchase, and it is of no use to you, you can always ask the seller for a cancellation. Sellers don't like a lot of lame excuses, - contrition generally works better with most folks. If the seller is kind enough to send you a Request for Cancellation, - you click to respond, click to agree, and you are no longer responsible for the purchase.
If, however, the seller decides not to offer you a cancellation, then you may have to choose between getting an Unpaid strike or just paying for the thing. You have probably already seen the following link about Cancellations, as well as the one about Unpaid Items, but I'll include them anyway:
http://pages.ebay.ca/help/sell/cancel-transaction-process.html
http://pages.ebay.ca/help/buy/questions/unpaid-item.html
Good luck. 🙂