Paige, 15, was reported missing in 2007. Despite her body having never been found, she was officially declared dead following an inquest in 2016.
Robert Ewing was jailed for life in 2015 following a trial at Preston Crown Court.
A spokesman for the Prison Service said the 68-year-old had been found dead in his cell on 4 November.
Ewing’s trial heard how he exploited the vulnerable teenager for his sexual gratification and then killed her when she threatened to go to the authorities.
Sentencing judge Mr Justice Jeremy Baker said “intelligent” and “devious” Ewing had carried out a “carefully planned and executed murder”.
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