Our local Goodwill store had an industrial machine for sale a couple of years ago, that I helped a friend shop for and buy.
The store manager had actually kept the bobbin case separately stored in a secure place, apart from the machine, because this piece could have so easily been taken out and stolen by shoppers.
I would never have thought about the possibility of someone swiping the bobbin case, but it makes sense that it could happen.
(Obviously the purchaser of the machine was given the bobbin case.)