20 years ago metal detectors were standard equipment.
We ran every sealed product though a metal detector. Being able to prove that there was no metal in the package when it left our factory kept us out of hot water with the FSIS more then once.
What happened after they were out of our control was something else.
You should see how long dairy sits in front of the dairy section before it is put into the proper refrigeration section. It takes me an hr if I have to walk the grocery store isles (back degeneration), and those same dairy units will be there the whole time. That does not included shipping and handling before and after it reaches the grocery store.
Don’t get me started on those dang misters, nasty bacteria makers.