I still think it's viable that the girls brought their bikes up to a garage and went inside a house.
We had two young girls that I don't know at all come up to our door and ask "where's the little boy that lives here?" They wanted to play flashlight tag with him, but the thing is, I had NEVER talked to them EVER- I've SEEN them around our neighborhood, but I DO NOT KNOW THEM- not even their names.
My son was at his dad's at the time, but as soon as it happened, I thought how easy it would be for someone to say something like "come on in, I'll go get him" and then Bang- they're inside, and there's no turning back for them.
Since they were going out to play flashlight tag, I doubt their parents would have thought much about it until they'd been gone for a bit, but someone could easily have had them inside totes by the time police would be called and I'd be willing to bet no one would have noticed anything out of the ordinary. It would have been a silent way to get two girls at one time.
Ever since the those two girls stopped by my house, the possibility the girls went inside a house has really stuck with me.