^^
You are right to suggest the mechanic is not the only guilty party in continental - his line management should also bear some responsibility and his work should be checked. But it is also clear that a licenced technician should never have been doing what he did.
From an airworthiness point of view bits should never fall off planes - as there us a direct hazard they will drop on someone and kill them. From a probability point of view you can never say never, so the probability of it happening should be consistent with a fatal outcome - I.e. 10x9 or similar - some expert may have the exact number.
On this basis, the continental aircraft was almost certainly rendered unairworthy as a result of the mechanics actions. Makes you wonder if it was a typical practice!