Sgt. Holstein, your code phrase for the Master Terminal is "Nuclear Dash." Show all those slowpokes how to keep the pace.
Before the Wastelanders update, Holstein's corpse, and thus this note, was found on the train tracks near the gate to the Big Bend Tunnel interior. When the Blue Ridge outpost was added with Wastelanders, Holstein's corpse was moved to be outside of the outpost, inside of the train car.