One of my first thoughts was if he was involved with the LS disappearance, and there has been no sign of her, why wouldn't he take this body to the same undiscovered location. But then I realized trying to apply logic to the mind of whatever this person is, may not be the wisest investigatory tactic.
But would that really be the logical thing he would do? Or would it be more logical he'd never visit that exact spot ever again, for any reason?
It does make you wonder though, and we aren't yet privy to any other biological evidence left at the scene, but if he doesn't leave the cell phone are investigators scratching their head and relying on her friends to come forward with info? If nothing else, it did drive home the possibility that someone may be out at nights looking for an easy mark.
It really does drive that point home and it does make you wonder what the theory (ies) would be if that phone wasn't there. Even with DNA evidence found (if there was any) I don't recall anything in his laundry list of past crimes that would necessarily mean there would be a sample of DNA in the database to compare any found at the crime scene to him. Fingerprints you'd expect would be, but that would assume he left any.