This is the exact spot.

Cape Otway GOW camping ground.
The koala you see to the right of my Contrail (early afternoon) moved eventually to a spot just above my tent and that is where it was when he rushed down from it and went to another tree about 10 meters away (found him there in the morning)
When I heard the "scream" I was too stunned to do anything for maybe a minute or so. It actually came to my mind that I heard a jaguar or something like that so I was not sure at all of what was happening.
(no, I had nothing to drink the night before...)
Now I wish that I had moved a bit faster.
My impression at the time is that the quoll (or whatever...) was chasing a prey , hence the initial rustling noise, and then close to my tent there was a confrontation and that is when the koala was disturbed.
(my two mates were sound asleep)
I did then go around the campsite with my torch but of course I had no idea of what I was looking for.
Now I would know to look for unfamiliar scat for a start...