Ideas ranged from a grandparent, aunt or uncle, to church people if she knew any, to school teachers or personnel, responsible families living nearby, or parents of her friends, and the like.
Also, I am on the other threads to say that if the guilty part(ies) are ever found, if there are any, they will be persons who have been in the VDs' home with their knowledge and consent, and probably in connection with swinging/sex.
If the guilty party is not connected to the swinging, I think the guilty party at least had knowledge of what was going on that night, and took advantage of the parents' "distraction".