Fucking hell my insights are late ones...
So I am working with fluid dynamics simulation. I went home fired up the laptop and started the calculations. This is how the events went:

9 PM: starting the calculation
10 PM: checking on the graphs to see whether everything will be alright if I leave it running. Then went to sleep.
2 AM: Waking up in shock, that I forgot to turn on autosave after every time step. Then reassured myself that this is only a test and I won't need the previous results anyway.
5 AM: waking up, everything seems to be fine. I pause the calculation hibernate the laptop and went to work.
6:40 AM on my way to the front door a stray thought struck into my mind... What if it lost contact with the licence server, while entering hibernated state. Bah never mind... It will establish a new connection when I switch it back on.
6.45 AM Switching on the laptop. Two error messages greet me.

1. Lost contact with license server.
2. Abnormal exit.

Looking on the tray the paused simulation is gone. Since I didn't enabled autosave, I have to start it all over again. Well. Lesson learned I guess. Too bad it cost 8 hours of CPU time.