I work with many Palo Alto investors who don't list their property on the MLS, they prefer to do private sales and will use an attorney to administrate the sale rather than a broker (I'm a broker and consult for a fee in these situations, but don't list the property for the client or negotiate the sale). They might put their own For Sale sign on the property or sell it through a network of buyers they already know. If you are truly interested in the property, call the seller or send them a letter and ask for all the details that you would normally see on an MLS printout.
It is possible the broker has not placed it in Trulia yet or the feed has not picked it up. Have you contacted a local Realtor or the listing agent about the property. Let me know if you need some assistance here.