Sorry to pipe in, but just adding my thoughts to this question asked, and hoping the original poster will also reply.
The available means that comes in every other missing child case, such as would automatically come with the publishing of names and photographs (of both the child and parents). In my view, there is *potentially* a whole whack of unmade calls in this case, which may have been present in other similar cases - people who knew them by their name, people who knew them by their appearance - potential witnesses to anything to all - witnesses to something, witnesses to nothing, just tips and clues, all to be interwoven together to make a big picture..
People who may have seen something, like say someone who saw the entire family of 4 sitting in the McDonald's restaurant on the way, or saw something other than that, etc., or people who saw the FD while in town at a certain time, or purchases made in Sydney, or whatever other tips and clues are a normal part of a missing person investigation. Even such things as identification of a vehicle, someone could have seen another vehicle which seemed to be following the family's vehicle, or people lurking about, but they have no idea that what they saw is even related to this case.
Not every clue has to be seen in a negative light for the FF - clues work both ways. People at the daycare from which the children were taken out early that day... who knew they were going - anyone? Who would know, if nobody even knows who the real caretakers of the missing boy were/are? There is nothing in the news to link the people known in their hometown of Sydney, with the terrible missing toddler tragedy in a tiny town 4 hours away. If the names of the FF had been published from the start, as they should have been, which also would have allowed for the foster children's names and their bio parents to be held in confidence as per FACS stipulations, who knows what information may have come to light that MAY have furthered the investigation in some way? The tiniest tip can start a chain reaction. We and they will never know. If 5 people called and said, yes, I knew they were heading there on the Friday, or 5 people called and said yes, I knew that Mrs.X's family was coming to visit on the Friday... then that in itself would give police a different tip, in that some people did in fact know the family were traveling there at a certain time. The possibilities are endless, and all of those potential possibilities are silenced due to the protection of the FP's names and faces. Instead we know all the grimey details about the bio parents, the ones whose names should have been private - not to mention photos and of the other siblings still in the care of the bios, etc. Everything is just backwards. imo.