Looks rather similar to the larva at http://lepidoptera.butterflyhouse.com.au/naco/smyriodes.html @galah681 :can you rear it in captivity to get an adult for idedentification of the species?
I will try to locate the tree it was on and find the leaf, but it may be difficult. What do I need to do to rear it in captivity? Would a jar with a lid with air holes be suitable?
Yes caterpillars can travel tens of metres overnight seeking more food or a pupation place. Best carry a little specimen bottle when on walkabout, to rescue them from predatory birds and wasps.