The fate of Moira Anderson is still a mystery after police said she was not buried in a plot at Old Monkland Cemetery in Coatbridge, North Lanarkshire.
Moira disappeared during a trip to shops in the town in 1957, when she was just 11.
It is widely believed she was abducted and murdered, but her body has never been found.
Moira's sisters were "hugely disappointed" by the blank drawn by detectives but officers vowed to carry on the hunt.
Sandra Brown, who believes her father abducted and killed Moira and who led efforts to see the burial plot searched by police, said at the graveside: "Both of Moira's sisters are hugely disappointed. It's been a long time and it's a shame their hopes are dashed.
"It's not what I would have liked to have happened but it's not the end of the story.
"Some people might think we've hit a brick wall here but I think we've actually punched through a brick wall. Over the past few months Moira's case has been upgraded from a missing person to a murder inquiry.
"It's become a cold case review and in the future there could be further developments."
Moira disappeared while running an errand for her grandmother on February 23, 1957.
She was last seen on a bus driven by convicted paedophile Alexander Gartshore, the father of Ms Brown.
Police had been investigating the possibility that Gartshore, who died in 2006, dumped the remains in the grave of an acquaintance, Sinclair Upton.
A radar imaging scan of the plot in 2007 uncovered inconsistencies in the soil that may have indicated the presence of an additional body. It is believed those images may have been of dislodged rock and debris.
Chief Inspector Kenny McLeod of Strathclyde Police said: "Despite today's outcome, the case will remain open. Any further lines of inquiry will be fully investigated."
Scotland's Lord Advocate, Frank Mulholland, ordered detectives to reopen the case as a murder last year.
Moira's sister Janet Hart, who lives in Australia, launched a petition to get the grave exhumed, believing Gartshore may have dumped her body there in the days before Mr Upton was buried.
An Airdrie sheriff granted the request and the Crown Office gave police the green light to begin drawing up an expert team trained in the techniques required for the delicate search.
A section of the cemetery was cordoned off with police tape on Tuesday and tents were erected around the excavation site as specialists carried out the work.
The operation was led by Professor Sue Black and a team from the forensic anthropology department at Dundee University.
Ms Brown believes her father was a paedophile "in the same mould as Jimmy Savile", who operated as part of a ring in central Scotland over decades.
She said: "We've had experts working with the police with the highest integrity but the people who did this crime were devious in the extreme and their wickedness knows no bounds.
"My belief is Moira is not far from us but she remains concealed by extremely wicked people. It's a difficult day but my thoughts are with the Upton family, who can hopefully have family members put to rest."
The excavation team started to fill the grave yesterday.
Ms Brown said: "The tide has turned.
"We are no longer in the 1960s and 1970s when people didn't discuss things like this.
"Victims are coming forward and there are more Moiras, believe you me, and we still have to try to find them."
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