Police vowed today to bring the killer of Becky Godden to justice.
The pledge came after the man who had confessed to her murder was jailed for life for a separate killing.
Christopher Halliwell, 48, had taken police to where Miss Godden's remains had been left at a Cotswold beauty spot.
But the murder charge he faced was withdrawn after a judge ruled Halliwell's confession to her murder was inadmissible because a senior detective breached strict police interview rules.
With Halliwell's jailing, Wiltshire Police have promised to catch her killer and revealed the last positive sighting of her was by a police officer on December 27 2002 in the Manchester Road area of Swindon.
Detective Chief Superintendent Kier Pritchard, head of protective services, appealed for any sightings of the young woman on or around that date.
"This very much remains a live investigation for Wiltshire Police," Mr Pritchard said.
"I have a fresh senior investigating officer appointed to that inquiry and we will pursue all lines of inquiry that we can to secure justice for the family of Becky Godden.
"Her family have showed great dignity and courage throughout the last 18 months.
"Clearly that has been an extremely distressful period for them and I recognise that and I am sorry for the distress and anguish that this would have caused them.
"We recognise that. But that does not remain the end at this point.
"Clearly the Independent Police Complaints Commission are reviewing certain circumstances that have been referred to them by Wiltshire Police.
"But sitting alongside that there is a live murder investigation and it clearly is our intention to bring Becky's killer to justice."
Nick Hawkins, chief crown prosecutor for the Crown Prosecution Service Wessex, said the most likely way of catching her killer would be if he confessed.
"We have explained to the family of Becky Godden that should further evidence in relation to her murder be brought to the attention of the police we will review this evidence again," he said.
"The investigation into her murder remains open.
"In reality the most likely compelling evidence that leads us to revisit it is if we had a legally admissible confession to somebody else.
"Forensic science goes a long way but we are dealing with a lady that was killed at least seven years ago.
"Had there been any forensic evidence that linked Mr Halliwell to Becky we would have used that already.
"We never know what advances there might be on forensic science."
Miss Godden was last seen alive more than eight years ago and her family thought she was living in the Bristol area.
It was not until police knocked on their door on what would have been her 29th birthday - April 4, 2011 - that they discovered the horrific truth.
Miss Godden, who had turned to prostitution after becoming addicted to heroin, had been murdered and buried in a field.