Deborah Pilgrim, 55, didn't return from a walk Sunday in Sedan, about 60 miles from Adelaide.
Police searched for three days. They used a chopper, drones, volunteers and several other adjacent agencies -- without success.
"Of course, with venomous reptiles around the place, if she had been snake struck, she would have been in all sorts of grief."
Before the fourth day of search and rescue, the police received some information from a man who has property in the area.
The man owns a block of the wilderness and has a surveillance camera on his property.
Because he knew authorities were looking for Pilgrim, he had been checking the footage more frequently.
On Wednesday, he noticed the letters S-O-S in a part of his property.
He notified police who found Pilgrim safe and sound in a shack where she had access to water.
She appeared in good health, but was taken to the hospital as a precaution, police said. She has since been released and is back home.