Thanks everybody for their time.

Luckily with my colleague (SharePoint geek) we were able to salvage document streams, their name, path and version... Well it costs us many hours of work which would not be necessary JUST if there would be water-tight backup. (There were NONE!) MDF had +/- 20GB, LDF 300 GB so guess what ...

Do backup, monitor backup, verify backup .. easy 😉