Posters and commentators keep circling back to "animal", yet it appears that there is no animal in the area capable of making a child disappear without a trace. Ie, this would require an animal large enough to remove the body far enough to take it outside the search perimeter or drag it underground, or to completely consume it. We're told there are no dingoes. There may be wild pigs in the area but none have (AFAIK) been mentioned specifically in this area.
There's a trope about domestic pigs being used to destroy a body without trace but in practice, while a pig can crush and consume most bones, it can't get its jaws open wide enough to get them around an adult skull to crush it. This may not be the case with a child's remains since the skull is obviously smaller and less rigid.
The question is therefore whether there are wild pigs in this particular area, but even if there were there would be some traces left behind, eg blood and clothing.