I've seen this reported intermittently - like every few months for a short period.
Sellers typically say it's a lag where the display corrects itself after a day.
Other sellers said if they open the listing and click on the # of bids, that, for some inexplicable reason, will move the listing from unsold to sold.
I suggest clicking the ? icon on the bottom right of the page @bubble-gum-cards to file a tech report. Or if you're on the app you can shake your device to trigger the same report screen.
