Trulia, like many internet base real estate information sources, is not an accurate source for sales information because Trulia does not have access to MLS records and you are correct in Texas being a non-disclosure state. Actual sales prices are only available to licensed agents and brokers and we are prohibited from releasing that information unless we have a client relationship with the party. I don't know the actual source of Trulia's sales information on this property, but this type of information usually comes from tax records of sales that do show the loan amount for the property. The Trulia lising that you quoted appears to combine information from a sale of the property in 2008 and the date that the current listing went under contract in January of 2009. Any information on the current sale will not even be entered in MLS until the sale closes and loan information can take up to a month to be entered in tax sources after the sale closes.
I feel your frustration with the information you are getting from Trulia and I appreciate you pointing out another error in their system. My best advice is remember that Trulia is a site that generates information, good and bad, for the purposed of creating internet traffic that advertisers pay for. While Trulia can be a good information source, it is a very unreliable property information source. Talk to a REALTOR and use the MLS system for the most accurate listing information and the best information for comparable prices on real estate.