Bottle holder broken during downhill

Has anyone seen something like this ?

Yesterday evening, I was riding downhill at about 50 km/h on a bumpy
road, with a stiff road bike with skinny tires (all these details to
tell you that it _was_ bumpy). Suddenly, I heard a big noise and
looking down I saw that my bottle holder was gone, together with a
nearly full aluminum bottle. The guy who was following 50 cm behind me
on a mountain bike (which I found foolish in the first place on such a
road) probably had the fear of his lifetime but did not crash. I don't
even know whether he was hit or not. But it happened so fast that if
he was not then it was just pure luck.
The bottle holder broke at the weld between the cage tubing and the
plate which is screwed to the frame.

I wouldn't like this to happen with me in the pack at the Sunday
morning club ride.

Turtle