I got a rear-tyre blowout recently using Conti GP5000S TR - near-slick tyre. Whilst I typically use these tubeless I had recently had a puncture and had to insert an inner-tube temporarily which I hadn't got around to replacing. After the blowout the tyre was irreparable as it had a 5mm tear on the tread, but when checking the inner tube my friend noticed that there was a sizeable stone inside the inner tube. I've tried to figure out how the hell the stone got in there!! The hole in the tyre was too small for the stone to pass through from the road. Even if it had, then it would've had to puncture the tyre, then the tube, and then insert itself into the tube fully within a split second.
I don't understand the physics of how that could be possible on a rotating wheel. Nothing stacks up for me. The best I can think of is that the stone was in there from manufacturing; but how the hell didn't I notice it when inserting the inner tube? I guess it's possible.
(The stone is shown in the photo)