As the ATSB are most heavily involved in the investigation I would first contact them, on the number you already have:
Report an accident or incident:
Aviation, Marine and Rail accident and incident notifications
Telephone ATSB (toll-free, 24 hours): 1800 011 034
Tel International (24 hours): +61 2 6230 4408
You may also consider making a report to your national authority, be it the AAIB (UK), NTSB (US) or other.
Bear in mind that false memories can be very, very powerful. Not recording the event in the log at the time doesn't help your case in that respect, but clearly it does not totally discount your testimony either.
That you word any reports carefully and make every effort to remain consistent is of course important. Telephone rather than email
will be taken more seriously, and writing down the events
as you remember them as fully as you can so you can work from a script when relating them would be a good idea - if you haven't already done so.
The reports of a 'plane on fire' seen so far have been largely discounted as being in the wrong area given what we now know about the flight path. That your route
takes you underneath the flight path gives your account a significance which theirs never had.
Contacting the ATSB and making no other public statements (bar this one) is perhaps the most 'professional' way to continue. Of course, anyone here can now send a link to this thread to any news agency so the matter is somewhat out of your hands unless you ask the mods to delete the thread. If PPRuNe gets a sniff of this thread (which is where most journos looking for aviation scoops hang out) then of course the music
will be brought whether you like it or not. If this is the way you want to go though, I can link this thread up to PPRuNe.