I sort of agree with Scott, all listings in an MLS don't go to online sites like Trulia or Zillow. Either the MLS itself or the agent's office must be set up to have listings automatically sent to online sites. Many MLS systems do this for their members, but the agent that listed it can select an option that did not allow the listing to be sent out. You need to ask them which it is. You do get what you pay for and if you just paid a submission fee to get listed they might have given you the FSBO option and not gone the extra mile for you.
In today's market I think most of what needs to be done is to get your listing out on the internet as that is where the vast majority of buyers are looking.
It is NOT automatically listed in Trulia UNLESS the agent or their company signs up for an automatic feed or enters the listing manually here on Trulia. Not all MLS listings automatically get listed on sites like this. When you hire an agent to place it on MLS, you get what you pay for and that is NOT MUCH. It takes more than placing a home in MLS for it to attract buyers.
The fact that it's in the MLS should mean it is automatically listed on Trulia through the MLS. It often takes a day or two for that to happen. If it doesn't, it may mean that the MLS you are listed in does not provide data to the aggregate sites.