Switching gears, I'm now leaning towards an answer as to why BG was there that day, and wonder if they may have been in contact with one or both girls on SM prior to that day.
A LE guy mentioned something early on in the case about parents knowing what their kids are up to on SM/online, or something similar. It's been mentioned that Libby had a Kik account, which I didn't know much about until I stumbled upon this just earlier:
http://foreverymom.com/mom-gold/my-...&utm_medium=Susannah&utm_campaign=Kik+account
According to that article, there are no parental controls which can be applied to Kik, and like other apps it can be applied to smart devices besides phones.
Could she or they have been stalked online? Here is info about Kik from Wiki:
https://en.wikipedia.org/wiki/Kik_Messenger
Good grief, what a nightmare for LE! I've alluded to the perp possibly using IP addresses from random public or online sources, along with a VPN or similar means to mask identity (location). All someone would have to do is use a smart TracFone, loaded up with minutes paid for with cash or with a cash card paid with cash, or other smart device, then set up a free e-mail account, then sign up for Kik. This may sound sophisticated to some, but really it is not.
As others wondered early on, were they there to meet somebody, somebody who turned out to be BG? I don't know how Kik works, but I wonder how many apps such as Kik/SC/etc. can be entwined, so images and messages appear on multiple platforms, simultaneously.