Sounds like an eBay ghost listing glitch. I have this same problem and did a search on ghost listings to find the information on how to report this to eBay. I reported the ghost listing to eBay. I also informed the high bidder that I no longer had this exact item but could send a similar one if that was OK.
You can either delete the item and take an eBay rating hit or ask the bidder to request a cancel due to this being a ghost listing. I do suggest you report the ghost listing to eBay, as this problem has occurred for years.
