Whomever this adult is who is harboring her is pretty savvy - had her discard her phone in Conway, managed to delete or disguise any communication during the planning of this, has evaded even the FBI for 2 months, etc. This person isn't stupid.
Sometimes the best way to stay under the radar is to be in plain sight. Who would think the new people who moved in down the street were being sought by the police. Shawn Hornbeck eventually was allowed sleepovers at his friend's house. And even when people commented on his resemblance, they didn't report it because it would be absurd for a kidnapped person to be visiting them.
Plus, around here (southern NH) I wouldn't know most of my neighbors. Our side of the street is woods. So I can't see many comings and goings during the day. The other side is more open, less trees, but it still is not a neighborhood. Even those that I do know or know their names or faces or cars, I don't know anything about them.
There are developments in town that are more like the neighborhoods people imagine, where everyone knows each other and the kids play together, at least initially, because they all moved in at the same time. But even friends who live in those developments have noted how much less of a community feeling it has as the kids grow up and houses turn over.
I think it would be incredibly easy for AH to be living anywhere without ever being seen by anyone. Not necessarily confined to the house, just someplace with privacy. As long as someone she is with has the money for food and fuel. Think of all the sparsely populated areas and the tiny cabins hidden in the Great North Woods.
The Yankee temperment could make it even harder to find AH. We discussed how New Englanders value our privacy before. We don't want to pry into people's private affairs. I heard the editor of Yankee magazine relate how he was asked in Minnesota about New Englanders being standoffish. He said that's not it, we just follow the golden rule. When new neighbors move in, we treat them the way we want to be treated and leave them alone.
All I can add to that is that I wouldn't even know my neighbors and I am a nice, friendly person. On a walk last year, I stopped in front of a house with a for sale sign 2 houses away from mine to greet what I thought was a new neighbor. Turns out it was the neighbor who was selling and had lived there longer than me (20+ years).
New Englanders would do anything to help someone in trouble but we don't want to interfer if things seem normal. My conclusion is it wouldn't take much for AH to be "hidden" in plain sight.