Were you able to find the listing on Trulia? If so, the listing agent information should be displayed towards the bottom of the Home Facts tab. If you're not able to find the property on Trulia (i.e. you have an incomplete address), then unfortunately I'm not sure there is anything you can do. It's not unusual to see incomplete addresses listed on Trulia.
I hope this is helpful!
Chad Gray PA, Realtor
Luxury Living Fort Lauderdale
Coldwell Banker Residential Real Estate
Is the property not in your MLS? Google search may be the way to go but I would say you should call the list agency (noted on the trulia listing page) and ask them for the list agent. Too many IDX pages in the results for me...