Very similar to Anderson's drawing of the larva of Termessa nivosa, see http://lepidoptera.butterflyhouse.com.au/arct/nivosa.html Perhaps it was feeding on algae or lichen on the twigs or branches of the bush. @clarehoneydove : any signs of lichen nearby ?
Yes I think Michael has the correct food plant. Lots of lichen in the area particularly bearded lichen. No idea which end is head, and did not collect as was out for a wander without a jar.