On August 27, 1974 their 15-year-old daughter Anna left their Lalor home for work in Thomastown. But she has never been seen again.

Desperately clinging to the possibility Anna would one day return, Mr and Mrs Banitskas stayed at the same house until old age saw them moved to a nursing home.

Even in sickness, the elderly couple insist their remaining sons and daughter keep the house in case she returns.

Anna's siblings Loretta Pentou, 48, Chris Banitskas, 58, and Peter Banitskas, 47, remembered her as  an "outgoing", "normal" teen who liked to sing along to the radio.

"She was happy, that's my memory of her," Loretta said.

On the day of her disappearance, Anna left home at 7am to catch a bus from nearby Kingsway Drive to her job at the Rolex Paper Products factory. Anna had left school in year nine to help support the family, who had migrated from Greece three years earlier.

On the morning she disappeared, her mother saw her packing some family photos and questioned her about it, but Anna said she just wanted to show them to her friends.

But these photos became a critical factor in the case, leading to suggestions Anna may have chosen to leave.

"It's been 40 years, you'd think if something was bad by now it should have been out there, so we think she might still be alive," Chris said.

On her mother's request, Loretta visited a psychic to try and find out what had happened to Anna.

The psychic said Anna was alive and living in Doncaster, but the family's hopes were dashed after a fruitless search of the area.

In Australia running away as a child isn't a crime, unlike in some jurisdictions of the US.

Each year about 35,000 people are reported missing across Australia, equalling one person every 15 minutes. But of these people, 95 per cent are located quickly, often within a week.

Missing Warrnambool man Michael Burn was found safe and well in Cavendish earlier this week.

Forty years on Anna's fate remains unknown, but time has not healed the loss felt by her sister and brothers.

"It's just like something's missing all the time," Loretta said as she welled with tears.

"It doesn't matter how many years have passed we still love her and still want her to come home if she's out there, or tell the police she doesn't want us to keep looking for her ... just something."

Detective senior constable Craig Hall said there were no leads in the case, but detectives were hoping to speak to a building contractor who had worked on a site near the Banitskas's home.

"The gentleman is elderly and I'm liaising through his son to arrange a time to speak to him," he said.

"I don't know where she is, that's why I'm appealing today to the public."

Anna would now be 55 years old, possibly with a family of her own. Her siblings are desperate to know what happened to her, but say they would not contact her if it was against her wishes.

When Anna went missing the eldest sibling Chris felt the burden of responsibility.

"I went through a lot. I got sick at one stage as well because of all of these pressures," he said.

"I had to comfort my parents as much as I could. I spent all these years doing that. Now it's time for her, if she's out there, please show yourself for Mum and Dad."