I hate to add to the wire brush worry, but it's not just BBQ. So many resturants use wire brushes. The last burrito I had was a few months ago. It had piece of wire in it. I kept the wire for a few days, and thought about it. The wire was not from a brush. I think it was old copper telephone wire. It that might have fell onto the grill from the ceiling, or wall? Anyways, I haven't had a burrito since that instance. A…
I bet you could do the same thing with fresh food, but I'm not sure it would be worth it. If nothing else, I don't think your typical metal detector is going to detect copper.
For my money, I'd like my local food-serving establishment to put the effort into hygiene.