Mark and Jacoba Tromp from Silvan, east of Melbourne, left their home with their three adult children to go on a holiday on Monday.
The couple was separated from the children in the Jenolan Caves area in the New South Wales central tablelands and reported missing on Tuesday.
Police said the children separated from their parents because they no longer wanted to continue with the holiday.
Mrs Tromp, 53, was found safe and well at the Yass hospital on Thursday morning, and has been assessed for stress-related health concerns.
NSW Police said she was taken to the hospital by a member of the public.
Police said the search would continue for 51-year-old Mr Tromp, whom they believe is in north-east Victoria after the car the family was travelling in was spotted at Wangaratta last night.
When the grey Peugeot station wagon was stopped by police, the driver, believed to be Mr Tromp, ran away into a nearby park.
Despite an extensive search of the area with the help of the Victoria Police dog squad, he was not found.
One of the children has been hospitalised in Goulburn with stress-related health issues.
Family under stress, son says
The couple’s son, Mitchell Tromp said the family — who operate a redcurrant farm in Silvan — was under stress.
He said the couple were paranoid just before they disappeared.
“It was a build–up of different, normal everyday events, pressure and it slowly got worse as the days went by,” he said.
Mitchell said his parents' behaviour was out of character and he wanted to see his father return home.
"I really want my Dad to be found, if everyone out there can keep an eye out for him," he said.
"He's not dangerous, he's my mate, he's my father. I love him, I just want someone to find him so we can bring him home."
Sergeant Mark Knight has described the incident as "the most bizarre case in 30 years".
He said when he went to the family's home on Tuesday he found the couple's personal possessions such as bank cards and mobile phones and paperwork all over the house.
"This is a really unusual case," he said.
"We know the family was obviously traumatised by something. We didn't know what it was."
This post originally appeared on ABC News.
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Is it's a mental health problem, but is out of character and affecting both parents over the last week or so, then this over-the-border holiday was sudden, and they were worried and paranoid about having technology like phones on them, plus the doors at their home were unlocked with documents everywhere ... then clearly something has happened to them, or someone is after them. Something serious. They are completely spooked.