Not necessarily. At a con like this, I've seen that walking up and talking to guys the creators of the works, like Steve Wang, is pretty common. It's more of a "Show and tell" style convention as they have their works out on display.
So if this guy who is "In the know" about Takaya is showcasing some of his works, he would be on the floor talking with people. And if the focus of the conversation was turned to Guyver, I can see it coming out if they indeed knew about it.
All that being said of course, it's still hearsay and not any kind of proof at all... But the situation described COULD have happened given the type of con and circumstances.