A video footage of a teenager recorded on the day she went missing about 13 years ago has been released for the first time to the public.
New shots of Charlene Downes, 14, who was last seen in Blackpool town center, were discovered during a trawl of CCTV. Her body has never been found.
Her mother Karen said she was "disgusted" the footage had only just been found after years spent investigating the unsolved murder case.
Lancashire Police said it "understood" Ms. Downes' views because nobody has been convicted over Charlene's death.
The footage has been released on the anniversary of Charlene's 2003 disappearance - as part of the forces "longest" murder investigation.
Ms. Downes said: "What I can't fathom is why this [the footage] was never found in the previous investigation. This is the bit I'm absolutely disgusted with.
"At the same time I'm happy with the footage and now hopefully they [the detectives] can move forward and we can get some answers.
"I want closure now... We can't move on with our lives and it's just terrible."
Detective Chief Inspector Richard McCutcheon said: "I can understand [the family's] views. We have just found the images and that's why we are publishing them now."
Charlene is shown with her sister Rebecca in Bank Hey Street at about 15:25 GMT on 1 November, 2003, walking towards the Coral Island amusement arcade.
She went home but returned to Blackpool town center later that evening and that was the last time Charlene was seen.
Police said the clothes she is wearing in the footage are the same as when she vanished.
Detective Superintendent Andy Webster said officers are looking at links between Charlene's disappearance and the "wider issue of child sexual exploitation" in Blackpool.
He said: "We have identified a number of people who could potentially be victims and offenders and we will be seeking to make arrests and prosecute abusers in the near future."
A judge cleared a man of Charlene's murder in 2008 after "grave doubts" were raised about evidence during his second trial. The jury in his first trial failed to reach a verdict.
A year later the Independent Police Complaints Commission (IPCC) said police evidence-gathering errors contributed to the retrial's collapse.
The IPCC found strategic and tactical failure in the management of the material and several officers were disciplined with one forced to resign in 2011.
But this resignation order was overturned by a 2012 Police Arbitration Tribunal.
New shots of Charlene Downes, 14, who was last seen in Blackpool town center, were discovered during a trawl of CCTV. Her body has never been found.
Her mother Karen said she was "disgusted" the footage had only just been found after years spent investigating the unsolved murder case.
Lancashire Police said it "understood" Ms. Downes' views because nobody has been convicted over Charlene's death.
The footage has been released on the anniversary of Charlene's 2003 disappearance - as part of the forces "longest" murder investigation.
Ms. Downes said: "What I can't fathom is why this [the footage] was never found in the previous investigation. This is the bit I'm absolutely disgusted with.
"At the same time I'm happy with the footage and now hopefully they [the detectives] can move forward and we can get some answers.
"I want closure now... We can't move on with our lives and it's just terrible."
Detective Chief Inspector Richard McCutcheon said: "I can understand [the family's] views. We have just found the images and that's why we are publishing them now."
Charlene is shown with her sister Rebecca in Bank Hey Street at about 15:25 GMT on 1 November, 2003, walking towards the Coral Island amusement arcade.
She went home but returned to Blackpool town center later that evening and that was the last time Charlene was seen.
Police said the clothes she is wearing in the footage are the same as when she vanished.
Detective Superintendent Andy Webster said officers are looking at links between Charlene's disappearance and the "wider issue of child sexual exploitation" in Blackpool.
He said: "We have identified a number of people who could potentially be victims and offenders and we will be seeking to make arrests and prosecute abusers in the near future."
A judge cleared a man of Charlene's murder in 2008 after "grave doubts" were raised about evidence during his second trial. The jury in his first trial failed to reach a verdict.
A year later the Independent Police Complaints Commission (IPCC) said police evidence-gathering errors contributed to the retrial's collapse.
The IPCC found strategic and tactical failure in the management of the material and several officers were disciplined with one forced to resign in 2011.
But this resignation order was overturned by a 2012 Police Arbitration Tribunal.