And if recent cases in this country are anything to go by then just as it appears nothing is happening...boom!...there's an arrest.
I think posters are speculating that the alleged assault charges may not have come directly from the child.
There is mandatory reporters in Australia so a teacher or sports coach could have notified authorities.
Way back a few threads, a very astute new member pointed out that the AVO was lodged by a homicide detective (as opposed to your local cop) and theorised that these charges came about from something overheard by surveillance (assuming the foster family is under surveillance).
I don't know if a child victim needs to confirm the abuse if asked by a teacher or police? But I wouldn't think so because a child could deny abuse through fear and intimidation, so I think charges could come about even if the child didn't report it or denied it. IMO.