1) The kidnapper would have had to see her far earlier in the day. Unless she was out playing in the streets closer to 2 AM.
2) He would have after seeing her had to follow her home and determine that it was her place of residence.
3) He would have then had to return to the home and break in without anyone waking (that is very possible)
4) He would have then had to manage his way directly to the girls room, making no mistakes and not entering the parents room by accident. (leading me to believe he knew what room to go to)
5) Upon entering the room and surprising the girls with his presence they would have had to remain silent from the get go. (Now who is going to wake up to a man with a gun in their room and not scream, especially a young girl, 2 of them!)
6) He would have then had to make his way out of the home with the girl putting up little to no struggle thus not awaking her parents.
7) The younger sister would have then had to sit there for 2 hours, silent, not fall asleep and then proceed to her parents room to tell them what happened. (I would think, if this actually happened she would not have waited 2 hours, though it is a very remote possibility.)
I am leaning very heavily toward her running off with someone she met on line, or a boyfriend. Though I have moved decidedly toward the online option.
Maybe the cops should talk with these people.
No dog?
Not really. If the house is for sale, they probably had an open house at some point.
Suspect looks at the house, sees the daughter's pictures on prominent display, and locates her her room as he takes the tour. He also has an opportunity to find a way into the house.
The chat room angle, if it plays out, also gives him a way to find out that she's moving, that she's having an open house, etc.
I really hope you're right, as it means she's probably alive and well. But I have a feeling she's a real kidnap victim, and probably no longer with us.