C'mon Griffo,
The only thing that your mind should boggle at it is what appears to me to again be some media misrepresentation...
In other words, without going into it too far, I would be stunned if the flight was other than an IFR flight (given the weather conditions in Cairns when the aircraft departed yesterday...) and it was conducted by the usual operator of the aircraft (mentioned above), therefore...
POB could simply have been established by a telephone call to the aircraft operator, or even better - given that you are required to state POB on taxi at a controlled aerodrome for CHTR flights, maybe our dilemma could have been solved with a phone call to Cairns ATC??
To be honest, I reckon the people that matter at AMSA / AusSAR etc would be in the know as to the POB.
You are barking up the wrong tree with the no SAR / no details scenario in this case - although I emphatically agree it is a weak course of action for pilots to take.
From what I see out my window this morning, a search is going to be difficult today. Hoping for the best, but sadly preparing for the worst.