On average: caterpillars walk at about 1 mm/second = 3.6 metres/hour or about 100 metres a day, so you need to examine all the foliage of all the plants in a 100 metre radius circle around where you first found it if you return a day later to look for it.
The caterpillars are known for only about 7% of Australian moth species. so about 93% of the time you need to take larvae into protective custody and rear them to the adult moth to identify their species.