He's probably related to someone important who would be really p**** about a beheading or whatever. Killing a Muslim....They're doing it everyday. That's no biggie to them.
They kill Muslims every day in bombings, but not in their more targeted killings. They actually released the Turkish group specfically because they were Muslim, according to one of the Turks who was released. (Also, I think, because the Turkish company had given in to the terrorists' demands that it leave Iraq.)
It's possible that they thought he was a Lebanese Christian, or also possible that his father's request that they release him because he was a Muslim and "not a fighter" would have made it look bad if they had killed him, especially if he was deserting anyway.
On the other hand, it's also possible that they have killed him and all of this is just a smokescreen.
Well, his blood is Lebanese. It seems the people of Lebanon would be pretty pissed if these terrorists killed him. That would result in a tremendous loss of support among the Lebanese for anything related to militant Islam.
The same logic was probably instrumental in the release of 3 Turkish captives last week. If they were killed, the terrorist would face increased hostility from the people of Turkey. When the Turkish workers were spared, the terrorist were seen by some Turks as compassionate Muslims.