Dr. Virgil's file is a paper note in Fallout 4.
On the table in the final memory inside Kellogg's brain in Dangerous Minds, after a Courser places it there. Cannot be read or taken, but used to access some of Kellogg's memories.
No transcript available, but the following memory is triggered by the file:
Kellogg: "If anything like this had ever happened before, I'd never heard of it. Maybe a sign that the old man was losing his grip."
Kellogg: "Finding someone in the Glowing Sea wasn't going to be any picnic, but I never expected an Institute egghead to give me so much trouble."