Yes, I had this scam pulled on me for an expensive purchase from another online selling site the Christmas before last. It's quite a sophisticated one, I've no idea where they get the used FedEx tracking codes from.
Have you opened an eBay item not received claim?
You'll need to state clearly in it that tracking shows delivery to an address that isn't yours, and also contact eBay and reiterate this to them and get them to check the tracking number whilst you're in touch with them so that they can see for themselves that the item has gone to a different address.