Search setback for Jason Richards and his girlfriend fears the worst

The dog, called Amy, was found wandering on a station near the Stuart Highway.

Station hands alerted South Australia police after the brown and white pointer-cross was found south of Glendambo, 120km west of where Mr Richards was last seen on July 21.

His father, Wayne, said a sighting of Mr Richards's navy Toyota HiLux utility was reported on Friday near where the dog was found, but there was no sign of the ute when police arrived at the location.

A robust hunting dog who was heavily pregnant when Mr Richards left Darwin three weeks ago to drive home to his family in Ballarat, Amy is now emaciated, with the outline of her ribs clearly visible. Her puppies are most probably dead after she gave birth somewhere in the outback.

Ms Laidlaw is in central South Australia with friends and relatives, searching for Mr Richards, who disappeared three weeks ago.

Police have already searched 4300 sq km to no avail. They even brought in an Aboriginal tracker.

Police yesterday described the case as "strange".

"It is odd Mr Richards' vehicle or himself have not been found," said Det Supt Grant Moyle of the SA major crime unit.

"I would have expected that if he was all right, if he had left that area and was still travelling, then we would have had some reports of his interactions with members of the public."

Police have consulted psychologists as they explore the theory that Mr Richards may have suffered a deranged episode linked to sleep deprivation.

Mr Richards, 29, vanished late last month on his journey home to Ballarat from Darwin, where he had been working as a glazier.

He was last seen on the Stuart Highway, south of Woomera.

Peter Falconio vanished on the same highway, about 1200km north, in July 2001.

Mr Richards' dog, Amy, was found alive on Sunday, about 100km from where he disappeared. Vets believe she gave birth a week ago to a litter of pups, which have not been found.

Ms Laidlaw said Mr Richards had no enemies.

The boat he was towing was found torched and abandoned the day he was last seen, June 21.

His father, Wayne, lives near the scene of the last sighting.