You should ask your agent. Any information given to you while your home is multiple listed from another agent without them being contacted by you directly would be a violation of ethics. You should ask your agent to find out why it is not showing up.
It all depends on your Realtor and how they decide to list your property. For a property to be listed on Trulia, your Realtor would need to put it on Trulia.
At Hunt Real Estate, we put all our listings on the big sites. The internet is now the way properties are found by buyers. I believe that if you can't be seen, you can't be sold. Trulia is one of many ways to be seen.