European explorers reached Kangaroo Island in the early 1800s and declared the Dudley Peninsula unoccupied - their entire methodology was watching the shoreline for smoke. No smoke, no people, case closed, log it in the ship record. The archaeological record says Aboriginal Australians had lived there as recently as 3,100 years before that, and possibly for 16,000 years total. They just werent lighting fires that particular week someone was looking. An entire continent got surveyed by whether anyone happened to be cooking dinner when the boat went past.