I think RA that monster in the shape of a human being killed most that are still missing. Maybe many were runaways, and were already being abused within the family unit or they could have given their parents so much grief that the parents/caregiver/guardian cut off contact. Or they never had a family unit in the first place, living in various foster and group homes. Maybe they had substance abuse parents. RA might have preyed on runaways offering them a place to stay, and knew they would not be missed if something happened. Preditors like RA can sniff out the desperation.