The Child Finder question

I really enjoyed this book, especially the way the author wrote the interchanging perspectives and the little connections that in some ways foreshadowed the clues.
The question I have is whether you found the fantasy world that Madison used as a coping mechanism believable? Do you think this could/has happened in real life to (child or adult) survivors of abduction or similar instances?
I understand that the premise is not necessarily based on real situations entirely but just wanted to see what everyone else thought!