This has happened to me as well this morning.
I had used the iPhone last evening (voice and data) around 9:00 Pm.
When I woke up this morning, I pressed the Touch ID and the screen reported that I had to re-enter the passcode since more than 48 hours had elapsed from the last time I unlocked the iPhone. How could 48 hours elapse if I last used the phone last evening?
I then entered the password (and I know it's correct as I use the same password on another iOS device) and the password does not work. After having to wait one minute after having so many failed password attempts, I called Apple Support.
I have a backup of the phone from September when I upgraded to iOS 9, and I never rely on an iOS device as a "backing store" for Messages (use a MacBook for that) so I would lose at most 30-45 days of images (no problems there), but something is not working properly.
Apple Support will be calling me back and will report back.