I forgot to wear my band last night as I slept, it was charging by the computer. I worked out and sync'd my band. Told me my calories, steps, and the 6 hours and 2 minutes I slept.
This sounds strange, but I would be sure to verify two things:
1. Are you sure you're seeing last night's data and not the last recorded sleep session from the last time you wore your Band to sleep?
2. Does the sleep session show a heart rate during the recorded sleep? My understanding is that heart rate is a key component in determining how deep your sleep was. If it did record sleep without being worn, it sounds like there could be an issue with your galvanic skin response sensor or heart rate monitor.