Oh gosh. It almost makes you terrified of using any implements along those lines. Honestly, I would've never looked for a failure mode like that. You're
exceedingly lucky.
I have a very distantly related story, although one that's much more benign (thankfully!). Years ago, there was a really nice grocery store in town (local chain) that would make fresh flour tortillas. Whenever we'd think about it, we'd usually stop by and buy a dozen or two. It ended for a few years when I was eating one of them and bit down into a washer that clearly had been pushed through some part of the machine such that it was slightly elongated, flattened, and very slightly sharp on one end. I was lucky in that I neither broke a tooth, swallowed it, or cut my gums; but you can imagine my surprise when I bit down and felt something lodge between my bottom molars. More so when I pulled it out and found a steel washer!
I still have that washer somewhere.
They eventually sold off their tortilla equipment, possibly also changing management. It's been upgraded in recent years with brand new machinery, and we started buying them occasionally, but I've since developed a slight paranoia whenever I eat food I haven't made myself. I'm a softer chewer now than I was in those days for that reason. :)