[Disappearance of Musa al-Sadr 1978]

Insha'Allah, he is alive but chances are high that he died, otherwise somebody would have found him in 2011.

Quote

 Qaddafi has been accused of, including the 1988 Lockerbie bombing (he essentially confirmed the guilt of the man convicted of the crime, Abdel Basset Ali al-Megrahi ) and the murder of Musa Sadr, an Iranian-Lebanese cleric who disappeared in Libya in 1978. (Omar said Sadr was beaten to death after daring to challenge Qaddafi at the dictator’s home on matters of theology.) He read about these cases in the intelligence archives, he said, which were easily accessible to those working in the unit. 

https://www.nytimes.com/2011/09/25/magazine/the-surreal-ruins-of-qaddafis-never-never-land.html 

Muammar Gaddafi was very notorious for making people "disappear" without a trace.^