I agree that scenario would be very strange. One would consider the 1st responder's immediate actions would be to sit down with whoever was in contact with William and go through timelines and William's character traits ie if he would wander and his personality type then the responder would report back to HQ to Macquarie local area command. I would imagine that FACS would have been contacted by police too.
I am not sure in my mind and in hindsight the 1st responder granting a neighbour permission to put out a social media alert so early was the right action. The scene became quickly contaminated with human scents, footprints, tyre tracks etc. The sniffer hounds would have become confused.
I believe FFC and MFC would then possibly have rejoined search parties coordinated by police or SES personnel.
I believe that the case was dealt with very badly at the beginning. It was simply dealt with as a child missing. No cars were searched, there were no road blocks and the caravan park was not searched, despite reports of a child crying.