IDX sites of Members
are all independent selections, plus there is a gating field to Display on Internet Y/N and whether the address can be displayed.
Your Realtor may not realize that one of these is set wrong or it may have slipped through the cracks. Most IDX fed sites will have the listing within 24 hours. A few save bandwidth by not pulling the listings so often from NTREIS or even by taking only the main picture and leaving other media untouched.
Though Trulia does have relationships with many MLSs, I'm afraid that not all listings are automatically sent to us. Many listings are submitted to us directly from brokers and agents. Please direct your agent or broker to the link below to submit your listing to Trulia and let us know if you have any other questions.
Check Realtor.com and Zillow. Same thing. They populate their data from our MLS.
Also, why don't you ask your Realtor? They are supposed to take care of the marketing of your house for you!!!
All the Best!