All of a sudden my iPhone can't find my Apple Watch.

When I go to the Bluetooth panel of Settings on the iPhone it says it's not connected. When I try to connected it says it couldn't find it and I should make sure it's turned on and nearby. It's on my wrist, fully charged, and turned on.

Any clues?

Update

Of course as soon as I posted this, the two devices found each other and are making happy. It always seems to work that way.