This is from Medscape (a site for medical professionals)
http://www.medscape.com/viewarticle/527730[...]However, it is important to note that ano-genital lesions that culture positive for HSV-1 in a child with a history of current or recent oral lesions may have been transmitted via auto-inoculation.Child Protective Services (CPS) may need to be informed that although the presence of the ano-genital herpes-1 lesions raises the concern of possible sexual abuse and an investigation needs to occur, it also is possible that the lesions were transmitted via auto-inoculation. Lesions that test positive for HSV-2 are not as likely to be transmitted via auto-inoculation. A positive culture for HSV-2 from an anogenital lesion raises a probable concern for sexual abuse (Adams, 2001). Heger, Emans, and Muram (2000) recommend that positive herpes cultures in children be subjected to confirmatory testing.
One thing that the original article does not say is what type of genital herpes the child had. The "cold sore" type CAN be manifested in the genitals via innocent transmission. Not as likely with the other type, but still can transmit without abuse.