*snipped for space*
Most adults know about DNA, in some form or fashion. A RSO would also know....definitely. Any criminal who has been convicted a felony. They would want to get the body as far away as possible to widen the area of suspects IF the body was ever recovered.
If it had been an adult, they had enough time to remove the body out of the MHP in plenty of time before LE got on the scene, no matter which timeline you use. They'd also take precautions to avoid any DNA getting on themselves and articles of clothing and their vehicle. Something as simple as an ice chest or rubber tote for a child that small to transport her out of the area.
I'm really leaning towards a perp who's made his first kill (transient or homeless ex con would have DNA on file, and wouldn't have the time to get the trust of the child). Inexperienced, not thought out well enough, possibly "stalking" or "observing" from a distance, but friendly with Jenise, and without access to transportation.
I try to put my head into the perp's mindset........and it just got pretty ugly so I'm done for the day.