Joan check the rules of your broker to broker exchange if the agent/broker is not a member of the local MLS you as the listing brokerage do not have to provide compensation to the selling broker.
Do you not have access to the MLS? That information should be there on just about any property you see on Trulia. If you're using Trulia as a substitute to the MLS, you will have to contact the listing agent/agency noted on the listing to make an appointment for a showing. As Joan stated, if the buyer you procured ends up buying, then if you're a licensed agent, you will get a commission.