Runaway's holotape is a holodisk in Fallout 4. It is recorded by an unnamed runaway girl, who was most likely from Sanctuary Hills, and chronicles a confrontation between herself and her parents that made them ashamed. As the altercation became more and more heated, she packed her things and retreated to a woodland cabin where she would play as a child. It is highly likely that the skeleton located in the cabin belongs to the runaway.
The holodisk can be found in the Ranger cabin, in a suitcase near the skeleton.
October 22, 2077.
I finally told them tonight, and it was bad. Real bad.
Dad was shouting, telling me I should be ashamed, that I had to get out of the house.
Mom just cried, and somehow that hurt worse than anything else.
She didn't say a word, not even when I packed my things.
I can't go to John-- he doesn't even know yet.
Maybe he'll never know.
If it weren't for the cabin I wouldn't have a place to sleep. Just need some time to think.
Last time I was here, I was just a little girl playing clubhouse in this old cabin.
Now I'm really scared.
Will anything ever be right again?