My watch disconnected from my phone this morning, so I had to reset and repair the watch. Pretty painless really, and I was quite prepared to set it all up from scratch. The nice thing is that I was given the option to restore from backup, so I did.
That's a pretty heavy bug for a device you have only owned for about 24 hours. Keep a tab on how often it happens, should it happen again in the next 24 hours I would contact Apple Support
Ya, I noticed a red "disconnected iPhone" icon at the top of my WATCH screen during the first hour of setting it up. I just toggled Airplane Mode on my iPhone as well as my WATCH and everything came back. Haven't had a problem since.