Well in my youth, that age, I could think of a lot of reasons to go back behind a building, smoke a joint, do a line, or do something else of that nature and not be seen or, take a leak, hate to admit but have done that in a dire emergency. She or he could of said "come back with me and be my look out so no one sees me". Or, to make out with him or who knows another encounter of that nature. No judgement, but if she willingly goes back and the footage doesn't show any struggle or been forced it's probably a reason along one of these lines. They picked a spot not to be seen, and it worked for him.
I think it was premeditated in the sense that this guy (my gut feeling) is a hunter and has probably done this before, was looking to do this to someone, but that the place and circumstance and most likely victim was not planned. He found a victim and one thing led to another for it to be the perfect opportunity.
It really wasn't until this case that I became aware of how many cameras may actually be on abandoned, boarded up or sites under construction. I was talking to a friend who converts apartment buildings to condos and he said first thing we do is put up surveillance and depending on the site, add dogs or a security guard because construction materials are constantly getting ripped off, or once they gut a building guys come in and grab the exposed copper plumbing old or new, etc. When a place is being worked on no one thinks when a construction truck or one of those white utility vans come by and stuff is going in and out.
I know there are cameras everywhere now. I was sitting in a cafe across from an el station and I could see 8 cameras that just blend into the background. But I had not really thought at all about an uninhabited place until now. Maybe he didn't either.
And to your point I sure hope they have earlier days and that day footage in case he did scope it out before hand or has been there before and we can get a clearer picture. But I think the one they have is pretty clear, doesn't someone know him????
And yes I want more info about the uber. I bet LE has more info about that.