The note can be found at ATLAS Observatory, overlooking Monongah. To find it, go up the wooden staircases that lead to the dome, but head straight north. The note will be on a railing, at a platform in between two metal staircases.
NOTE TO SELF:
They put railings on high places for a reason, Dorsey. Almost fell slipping on a wet patch after the rain.
Goes to the back of the queue, though. I don't expect to be working up here too much, and there's more critical stuff to do.
Playstation 4 When inspected, this note may display at an unusually slanted angle.[verification overdue]