There may be small pockets of these creatures left or just some stories of things that were there awhile ago.
After being to Australia and staying in several remote farm steds (not sure if that is the correct term) with small groups of mostly isolated people (nearest store 80KM away) then I can understand that you get worried with the noises the night makes! I heard stuff bigger then a horse smashing its way through the jungle some nights! And occasionally a deep rhythmic beating noise! It would scare me and the people I was working for, on one of the farms they had me clear all the undergrowth and small trees out for nearly half a mile away in all directions from the house.
If you have never seen such massive areas of unexplored subtropical or tropical rain forest then you will understand there could be a whole lot of big stuff living there that we have no idea about.
LOL Bet the big creature crashing through was a roo or a cow. It might have even been a horse. I would say the deep rhythmic beating was frogs. They get quite a sound up when they manage to get into unison. Did you hear Koalas mating? That sound will send chills down your spine Funny how such a big scary sound comes from such a cute cuddly looking little thing.
What part where you in?