Jake's note is a paper note in Fallout 76. It is written by Jake Miller.
The note can be found at the Pleasant Valley cabins, behind the tavern near a Port-A-Diner, only during the quest Seeker of Mysteries.
You sure you don't want in? Hawke said those girls never hit the same checkpoint twice. That makes North safer than wherever it is they have you these days. Think on it, all right?