This is how I see it panning out. He parks up, intent on some form of deviancy. By the way I don't think he will be a burglar for gain, more of an intrusion/perverted kind of thing of some kind. He hears Libby. Goes to look. Back to car to think it through. Possibly adjusts trousers, let's not think about why. Has a smoke. Waits for privacy. Goes back and takes her (awful thought in every way). He has seen an opportunity to escalate. Risk taking matches flashing, voyeurism, break ins...
Police start investigating. He crosses their radar. Maybe previous, maybe car related, but efit will arouse suspicions. Photos made public. Victims recognise him and come forward. Maybe a previous offence was near park bench and they look for any possibility of dna.
I believe he took Libby. What are the chances of a sexual predator in that location, giving her a lift home and she made advances??? No way.