Here is the thing though... everyone makes mistakes.
Having worked for many years in aircraft maintenance, from flight-line level right through to depot level, where an aircraft is all but ripped down to its stingers, spars and frame, and reassembled, I can easily see how such a mistake can be made. A person whose job its to do task "A" (in this case, fit the door plug bolts) gets distracted by a boss or a shift foreman, who says he will assign someone else to do the task because he needs this guy to do another important job. Another important job comes up and the second person get re-tasked to do something else, and so on. Then someone else comes along whose task it is to put the interior paneling back on. They will reason that they wouldn't have been tasked to do that if the job was not ready to be covered. They fit the paneling. The original guy, or the replacement comes along to finish fitting the door plug and finds the paneling in place and figures the boss must have assigned someone else to do the job. The mistake has been made - the door plug is now missing the bolts, and no-one knows about it.
Now, in a firm with quality and safety as core aspects of the work culture, someone will check the work before the covers are put back on. The person putting the covers on will ask a supervisor to check before proceeding. Whenever I had a task that involved a panel covering any work I had done, I would always get a supervisor to sign off that the work was done before I would allow that panel to be refitted.
Quality and safety is an attitude, and that attitude comes down from the management. If the management treat the workers like ****, if they fob them off when they try to report safety issues, if they tell them to never put anything in writing, if they make life harder for those who persist in reporting safety issues, those workers will soon learn that the management don't give a ****, so they will rightly reason that they don't need to give a **** either.
