Does that agent have a "Premier Agent" tag next to their name? Both Trulia and Zillow allow agents to pay monthly fees for advertising and give them "Premier Agent" status. This means that Zillow and Trulia have a default checkmark next to a Premier Agent and make it convenient for buyers to just fill out the "Contact Form" and click "Submit." Buyers would have to uncheck the agent with the default checkmark and put a checkmark next to your name, then fill out the Contact form and click Submit. Most buyers never bother to fix the checkmark which makes it easy for Premier Agents who appear on your listing to get all your leads. Many realtors hate it but it's the primary revenue source for Zillow and Trulia.
I was a Premier Agent on Zillow so yes I'm guilty of receiving calls, texts and emails from buyers who asked about properties that were not mine.