The note can be found at Wade Airport, inside of the main airport terminal, on the ground, near the crashed vertibird, in the hand of a skeleton.
Grandpa, this is Chase. If you come back to get me and somehow happen to find this note, I headed for Charleston. I was going to wait for you, but there are some people heading out now and they said I shouldn't stay because it's dangerous here. I'm leaving the note where you left me, so hopefully you find it. Please come find me, Grandpa.