Watch ran out of battery while sleeping and sleep tracking is completely missing

[2b2bff]

Usually if the battery runs low my Race S comes with “Trainierst du bald?”. Not so yesterday. I looked at the battery state by chance and it was at about 11%. I thought, okay, I charge it in the morning.
Next day I woke up a bit late and watch greeted me with a “charge now symbolic”. Probably because of low battery my watch hasn’t vibrated to wake me.

After charging it and syncing to Suunto App, I can see that my heart rate has been tracked right before the point I woke up, My Resources stopped about half an hour earlier. However the complete night is missing in sleep tracking. Not just the segment after my watch decided that it has a too low charge.

Why on eath has Suunto App - or the watch - decided to completely skip sleep tracking and not just take the already recorded part and skip the rest?

Is there a way to get the missing data?