what probably happened is that the ship was attacked by pirates- probably a stray cluster missile given that if pirates really deliberately attacked it, it would've been destroyed for sure. there was probably a pirate/player battle going on nearby or pirate/trader battle, and some of the pirate ships perhaps used cluster missiles, and one of those missiles selected the miner as a target.
lesson: never disconnect with an undocked ship in use. next time alkjato please dock the ship to homebase before you log off.