Quality Control Issue?

My buddy's mom had a New 70 Buick Skylark with a rattle going over bumps. No one could figure it out. 4 years later I'm under the car doing exhaust work and see something through one of the frame holes. A beer bottle ! I broke it up with a piece of threaded rod . No more rattle. We thought Disgruntled or Friday drinking but as said maybe (UAW) .