The Stash Note is on a counter near the far end of the second floor of the coffee shop where the hunters build their bridge, just before you enter the hotel in Pittsburgh.
The writer says the attack on the Eastern Checkpoint happens tonight and that extra supplies are hidden at the Regal Apartments behind a red X.
Look out for a door marked with a red X beside a blue truck in the area before the hotel; the Mother's Letter waits behind it, behind a shiv lock.
Abandon Zone Note
The Abandon Zone Note sits on the desk in the office at the far left end of the bookstore's first floor in Pittsburgh.
Accretion
Accretion, issue 6 of Savage Starlight, sits on a coffee table in a lounge on the second floor of the Hotel Grand, during the Hotel Lobby section of Pittsburgh.
Ambush Map
The Ambush Map is pinned to the wall of the room at the end of the hallway. Leave the stairs in the room with the two dead bodies, follow the corridor to its end and look on the wall.
Applicant Checklist
The Applicant Checklist is under the stairs on the far left of the bookstore's ground floor in Pittsburgh.