[ He takes it and feels it by rubbing it with his fingers. There's nothing particular special about it and when he flips it over, it's blank on the other side. ]

I can't say for certain, but it's possible. There are some beings who can sense Personas and although they can't get the exact details, they can get a basic understanding of the Persona.

[ It's rare to find someone like that, but it's definitely something that is plausible. Souji carries multiple Personas, even excluding his guests', and his ultimate is far more powerful than everyone else's. That could be a telling sign. ]