Jeremy isn't much help here; he either can't remember or refuses to think about it. We'll need to find out on our own.
Jeremy asked you to bring him his notebook from his office at the City Post. That seems like a good place to start.
The receptionist very rightly won't let Rosa into Jeremy's office, but she can't stop someone she can't see, especially if that someone can float through locked doors.
As Joey, go upstairs into the room marked "Junior Reporters." Jeremy's computer is the one in the middle of the room with a notebook leaning against it.
You can't do anything with the notebook -- Joey's blowing just rustles the pages -- but there's a post-it on the computer. Right-click on that to read it.
If that's Jeremy's last appointment, it's significant. Leave the newspaper and go to High Line (which is a park on an old elevated train platform in New York).
How do I get Durkin to trust me?