luke shambrook was last seen leaving candlebark campground on friday .
there has been an unconfirmed sighting of luke with police acting quickly .
the 11-year-old was reportedly seen walking 4 kms from his campsite .
police remain hopeful they will find luke , who has ` high pain tolerance '
luke has limited speech and his family says he is probably confused .
a large search is being carried by a medley of search and rescue teams .
police also said conditions are favourable for his survival overnight .
they have issued an extensive description of luke and his clothing .