The Facebook page can be viewed here: The case of missing girl Sherrlynn Leigh Mitchell

A family friend of Sherrlynn Mitchell, Alex Girle, set up the page last week in an effort to put pressure on police to further investigate the disappearance of the then 16-year-old, who was last seen waiting for a bus on November 22, 1973.

"I feel for Sherrlynn's family, particularly her mother. The not knowing would be terrible," Ms Girle said from her New South Wales home yesterday.

"I gave this a lot of thought before I set it up. I had a child who died, but it would be the not knowing that I couldn't stand."

Ms Girle's baby daughter died from Sudden Infant Death Syndrome in 2003. Another daughter, aged in her teens, has also been a run-away, but has since returned.

"Sherrlynn's family still holds out hope that one day she will be found," Ms Girle said.

"There are still a lot of unanswered questions, so by starting up this page, I hope to put pressure on police to do more about their investigation into this case.

"If Sherrlynn is still alive, I hope she may see this Facebook page, or I want someone who knows something to come forward."