The family of Allison McGarrigle has described her as "the best mum in the world" as her two killers were jailed for life.
Convicted paedophiles Charles O'Neill, 47, and William Lauchlan, 33, were sentenced to a minimum of 30 and 26 years respectively for murdering her in 1997.
In a statement, the family of 39-year-old Mrs McGarrigle said: "Lauchlan and O'Neill have taken away the best mum in the world.
"Allison McGarrigle was a bubbly, happy woman with a heart of gold.
"She loved children and she was taken from us trying to protect a young boy from abuse.
"For many years, we have had to live with not knowing what had happened to her.
"But we knew she was not just missing; if she was still alive she would never have left her three kids or missed out on watching her four grandchildren grow up.
"We miss her terribly and wish that we could lay her to rest."
Lauchlan and O'Neill are believed to have strangled Mrs McGarrigle in 1997 to prevent her reporting the abuse of a young boy.
It is thought they put her body in a wheelie bin and dumped it in the Firth of Clyde.
After their conviction, it emerged that the pair were "predatory paedophiles" who had convictions dating back to 1998.
They were also sentenced for 10 years each in prison for abusing a 14-year-old from Irvine, Ayrshire, a 15-year-old in Spain and grooming a six-year-old in Scotland at various times between 2003 and 2008.
They were found guilty of these charges at the High Court in Glasgow last month, before the murder trial began.
Jailing the pair, trial judge Lord Pentland said they had "conceived a callous and depraved plan to murder (Mrs McGarrigle) and to dispose of her body.
He said: "You then put this plan into effect with chilling composure. You went to great lengths to cover your tracks.
"You must have thought, for some time, that you had succeeded in escaping detection since to this day Mrs McGarrigle's body has - tragically - not been recovered."
Lord Pentland said that the "consistent theme" in both their trials was the "calculating and devious manipulation of vulnerable individuals in order to further your appetites for sexually abusing young men and boys".
He warned them that they may never be released from prison.
Lauchlan and O'Neill were arrested in 2008 after a joint surveillance operation by Lancashire and Central Scotland Police discovered they were grooming a six-year-old boy with intent to abuse him.
The police operation also involved Strathclyde Police, Lothian and Borders Police and Fife Constabulary.
Following the verdict, Det Sup David Wilson, from Central Scotland Police, said: "Our inquiry into the grooming of a boy from the Forth Valley area was one of the most complex of this nature we have carried out.
"When we were alerted to the fact that O'Neill and Lauchlan were targeting a family in our area we put in place measures to disrupt and stop them, working closely with the other forces.
"That co-ordination led to the men being charged with previous sexual offences and then with murder."
The family of the six-year-old boy who was "groomed" for sexual abuse by Lauchlan and O'Neill also spoke of their relief that the pair were in prison.
In a statement, the family said: "Lauchlan and O'Neill befriended us through a third party and they seemed like a genuine couple.
"When they showered us with gifts, we began to suspect their motives and we contemplated phoning the police. We decided not to - a decision we regretted after finding out who they really were.
"We would like to urge any family who suspects anyone who has contact with children to please get in touch with the police."