As usual, I had an idea!
I'd be interested in knowing if someone who recently moved close to Jessica came from the area where the backpack was left (the house next door to her friend was just sold/bought in May, but I'm sure there are others). It's a long shot, again, but I was thinking that it could be a guy who was caught abusing his ~10 year-old blonde haired, blue-eyed daughter, and his wife kicked him out refusing to allow him to see the girl again (but never called the police because of embarrassment or some other weird reason.) It could be that JR reminded him of his daughter, but after abducting her, his anger at the daughter for telling on him took over. He may have killed her in a fit of rage, but actually calmed down before planning to dispose of the body and her belongings.
He may have left the backpack close to his ex-wife's house thinking in his sick mind that she'd know it was from him and she'd feel guilt for making him kill the girl. I haven't quite figured out why he would have done what he did to the body, but one extremely sick thought I had was that he wanted part of her as a reminder of his daughter. If nobody fits in either place, maybe it's someone who is moving to Superior from Westminster. Or maybe I just need to give it a rest for a while, I can't believe how moebid I'm getting.