$#$%!!!
Well, it turned out to not be a stone and the worst case – bearings.
The outer bearing had completely disintegrated. I was lucky – the spindle had got so hot that the bearing had welded itself to the spindle. The wheel could have come off completely had it got any worse.
Not only was the bearing toast, it took the spindle with it, and the bearing race on the rotor (brake disc) too.
