Bringing this over from the other thread, because I meant to post it here....
I hope the PI gives us some answers by tracking things like the homeless guy or handyman, who is now absent from the neighborhood, and who raises my hinky meter, because it reminds me of the Elizabeth Smart case. Even though that guy had been inside the house and there's no evidence this guy had (that the family knows of).
In the Smart case, that guy came into a house at night that was absolutely full of people. Into a bedroom with another young girl, and got Elizabeth out of the house and kept her quite nearby in the woods with searchers right nearby. In this case, an advantage might be that a younger child would be harder to threaten and more likely just to cry - unless she was drugged.
But the possibility of someone who was watching the house and waiting is real to me.
Also, I think people overstate the whole "whoever it was knew the layout" thing. Frankly, the house isn't that large and there aren't that many possibilities about where the bedrooms would be. Anyone watching the house could figure out where the kitchen is, bedrooms, etc. As someone noted upthread, even a juvenile burglar, really anyone who's been in a few homes, can be in and out in no time.