Actually a number of Civilian Jets have been hit by SAMs and not downed. That is the beauty of pod mounted engines vs internal engines like a fighter would have.
I know of at least 2 corporate jets that were struck by stinger type missles. They DIrectly impacted the engine destroying it, but the damage was more or less contained in the engine and the aircraft limped home on one engine.
Its one of the reason's that I don't believe the Missle Thoery of TWA...
Cheers
Wino