I doesn't matter whether they expect anyone to believe it, or if anyone believes it; both are irrelevant. The only relevant fact is no paperwork. Belief has nothing to do with it. Either they produce it, or they don't. Whether someone believes it was lost, the dog ate it, space alients absconded with it, or it was the victim of spontaneous combustion is irrelevant.

Boeing doesn't need belief. All Boeing needs to do is not produce the documentation.

Boeing is not the government. Boeing sells things to the government. Boeing is a contractor. Boeing does not tell the FAA what to do or dictate the time of day.