Welcome to Trulia and thank you for your question. If you can let us know which listing is currently showing incorrect agent information, we can fix that. Please either send that information to us via the link below or use the 'Report an error' link that you find on the property details page to do so.
MRIS currently does send listing information to us so I'm not sure why one of their listings would be missing from our site. I encourage you to contact MRIS directly to ensure that they are including the particular listing in question in the data feed they send to us. Once they do so the listing should automatically display on our site thereafter.