No, not exaggerating. Some of them have been my own students, some of them have been friends, or friends of friends. I almost did it too. Made my dummies so I could practice using the TV as the backstop (and the cement wall behind). I made sure no live ammo in the room and commenced tap rack drills and others. Once I'd worked through a mag I'd pick the rounds up off the floor and start over. One round bounced under the couch, lifted corner of couch up and grabbed it, and loaded it in the mag. I noticed it had a non dinted primer. Thought, hmmm. took another look. Hmmmm???? lifted couch, oh look at that, there's the one with the fired primer. Put the other one in my range bag, took to range and yup, it fired. I guess a cat found it in the laundry room or something, I really don't know, but it ended up under my couch. Since then I've run the bright orange tips of plastic and nice polished nickel case. No mistaking those.
Well not quite true, CSC managed to mistake one of those and punch a round through the wall in the office upstairs at the club and take out the monitor I was going to be sitting at 1/2 hr later doing some computer stuff.
With 15 years of teaching a class pretty much every week and averaging in 15 people a week, I've had a lot students, I explain the above to them, and it doesn't always take. People get complacent at home, which is the single biggest accident causer. I see it all the time at the range too from just drop ins, to high level competitive shooters.