I've never ingested one, but I've spotted and removed bristles on my grills several times. I stopped using them awhile ago. It's only a matter of time before someone swallows one.
The more grill is heat, the higher chance wires come off the melting plastic. I've also noticed this before. Since then I was preheating the grill a bit, shut down the fire, clean up with the brush, heat and cook.
I'll probably go with the Argentinian circus people way of cleaning the grill starting from now.
I already do something similar, with a ball of aluminum foil soaked in water and tongs. I will switch to the "Argentinian circus people way" of doing it, and will call it that, and tell all my guests that's what it's called, forever.
