I agree. Maybe someone found the rain the window of opportunity to get Sierra in the car with him/her/them. Someone she felt comfortable going with. Possibly a classmate or an acquaintance from the neighborhood. I am thinking they would have lived close by since it would have looked suspicious for someone far away just showing up unless there is a record of someone texting her about a ride. But nothing like that has been released. How long had she been at the new school?
I have to agree with the possibility that it may have been someone living in the area...possibly, someone very close to her home, who'd see her heading for the bus at some point or another along her route every day and possibly known her schedule as well as her mom's and the mother's boyfriend's schedules so as not to be caught.
In my personal opinion, it would likely be someone who wasn't considered "suspicious" to have been in a vehicle at that time in the morning, out the front of her home (since the dogs lost the scent at the end of the driveway). That cul-de-sac that she lives on, is one where general traffic wouldn't normally be traveling down so, it likely didn't get a lot of traffic other than those who lived there so, any "strange vehicle" might have caught someone's eye. To me, a stranger with abduction in mind, likely wouldn't have just "happened" to pass by her home to see and abduct her.
Having said that, it would seem that perhaps, someone she knew...even slightly...from the area, might have offered her a ride to school that morning and with the rain, she decided to accept (hair done, make-up etc.).
I doubt that she was going to run or even go away for the weekend with a friend (male or female). She seemed to have had a fairly decent relationship with her mom. Besides, a girl that age would have likely packed more than one clothing change, the charger for her phone and make-up...perhaps, deodorant, tooth brush, etc.. (At least, I didn't see those items listed...or, have I missed something and they were found in her bag???)
I'm leaning towards the idea of someone she knew, older...likely by quite a bit, and male. Because of the phone being tossed and then, the bag, I'd be willing to bet that it was someone who took the phone from her hands and tossed it out the driver's side window. The bag....well, it seems possible to me that he told her to toss the bag or he would.
Wonder if all neighbors have been checked out yet?
Of course, this is all purely my own thinking and nothing else:waitasec:.