The Autobots were supposed to be the only ones with human 'pets. Decepticons knew that. But, when the Communications Officer Soundwave needed to send backup to an energon mine out in the Rockies that was infiltrated by Autobots, He realized he would have to get his servos dirty, which he has no problem with. But on his way to the mine, he came across an unconscious human child high up the mountain. They looked no older than sixteen and were pretty beat up.
He wasn't sure why, but he felt concern for the human. It might've been the fact they were unconscious and at the mercy of the elements, or the fact it was a child who was left behind. Either way, he decided he would bring the child back to the base, maybe let it be a living petri dish for Knockout or Shockwave, he didn't know, and he didn't like either. He set them down until he was done with the Autobots.
Once the Autobots retreated, he went back to where he put the still-unconscious child and opened a groundbridge back to the Nemesis, hoping he'd be able to warm them up enough so they're conscious again.