Hard to imagine how this little guy in a bright coloured outfit could not have surfaced with two hundred people searching for him in a one and a half and up to ten kilometre radius for three days and nights!
Some thoughts:
I have not seen images of his parent/s on any news reports but have heard that both parents are helping with the search. That's a good start. At least that points to both parents being on the scene and it should discount any theory that one parent might have abducted William.
Like others have mentioned upthread, I cannot quite get my head around what appeal the thick bush would have for a little boy, when he is at his grandmother's home and playing with a sister! All I keep hearing is that he was playing with 'a sister' - I have not heard it mentioned whether she was older or younger or could have been in any position to indicate where he might have gotten to.
As for a potential abduction: isn't that a fairly unlikely place for something like that to occur? Who would just hang out there, waiting for a kid to turn up and abduct them? It's not like it's outside a school or in a shopping centre. How could anyone have known that William would be there, playing in the front garden, at that precise moment, and not under the watchful eye of an adult? It's not like it's even his home address! He was on a VISIT to his grandmother's place.
If it WAS an abduction, then it would raise the question as to whether someone known to the family would have done it. In other words, someone who would have had some prior indication that William would be there that day.
And, yes, the lack of a scent beyond the property is weird ...