It could be an older listing that has not yet been removed. I suggest flagging the listing on the site to alert it to a Trulia moderator and contact them by sending an email message to: http://www.trulia.com/help/ask. They usually respond within 48 hours.
You can also call Trulia M-F from 7:00am-4:00pm PST at 888-466-3501 to request that the status be changed.
Trulia aggregates data feeds from around the country. Often, it's not updated once it's on Trulia. So, if your house had been purchased in the past couple of years, then it may still be listed on Trulia, even as a for sale listing.