Jessica, I was working on MLS when I saw your question and I checked as well... it is showing as sold in 2006 like you mentioned. The only other explanation I can offer is that it could be a FSBO where the owner has used a company to help market it on-line. There are a couple of homes where I live that are FSBO's and are on Trulia. They have a MLS number on their page, but it isn't an Austin MLS and those homes do not show up in our MLS.
I think that sellers think it's a great idea and will save them money. The downside is that the 7000+ Realtor's cannot get their information and can't show their buyers the home - no MLS + no Lockbox + no Information = a No Show!
My advise would be to call the owner and just ask! :)
Stacey Rider, Realtor
Bartlett Real Estate Group