The best person to ask this question to is your listing agent. Trulia will not permit a property owner to list list on the site directly. It may only be listed by an agent. Typically listings are fed to Trulia through a variety of sources but it's possible that your agent or agency elects not to participate with third party sites such as Trulia, Zillow, etc. It's also possible that if you just listed a day or two ago that it simply hasn't been picked up yet.
Speak to your agent and ask.