I am 100% behind the parents, there is nothing but nothing to make me think anything is hinky about either one of them. They seem a loving normal couple with kids they adore.
The creeps who do this sort of thing are completely brazen, look at Kienan Heberts kidnapper who not only took him but returned him to his living room right under LE's nose. (thank god he did too). John Couey walked into a house with a dog and two sleeping adults and quietly took Jessica Lunsford while Elizabeth Smart and Polly Klaas's kidnappers had a house full and in one case left a live witness. These guys fixate on someone, it isn't just to get a kid but to get the kid they want they are willing to do whatever it takes and they believe they are invincible..which in a way they are bc their chutzpah allows them to get in and out with a child. Joeseph Duncan took Shasta into a gas station store with full video/security cameras after her kidnapping and then to a Dennys.
This mystery figure could easily be the kidnapper.. Even with a wall there, you are talking a six year old frightened out of her wits by a man in her bedroom probably with a knife or weapon who imo is telling her if she makes a sound or doesn't cooperate he will kill her parents and brothers. As an adult I might go with him quietly to keep my family safe, as a six year old there is no question about it. Scale a wall or climb out the window, she would do as she is told. He could push her up over the wall in a minute and she would wait til he climbed over himself, terrified to do anything but what she is told.
Plus the coincidence of a lurking man avoiding being seen the night a girl goes missing just a short walk from her house is to high for me.
imo