Smartwatch Sleep Question

[Hawkmoth]

I have an android smart watch. When I don't set it to sleep, it guesses based on when I put my phone down last thing at night.

Normally, it gives a wake up time 1 minute before my alarm goes off.

One day last week this time was about 20 minutes before my alarm went off. That day I slept through my alarm. Is this likely to mean that somebody else unlocked my phone while I was asleep?

I dont understand what you mean
Does the smart watch not track your sleep using the watch?
Why would you think someone unlocked your phone?

The watch only does the full tracking if you press the sleep button on it. If you don't, Android Sleep guesses the time for you based on your phone activity. That's obviously not as useful, it's just the time without all the other data.

Why do I think someone has been through my phone? I went out wearing a nice coat, makeup and heels.

The phone had moved... would it have ended my 'sleep' just by movement, or would it have to be unlocked. I can think of no reason for it to have been moved at the time it recorded, nobody is generally up by then.