アップルウオッチの探すについて

Unless the watch connects to a Wi-Fi or Bluetooth network, the watch can not be located, or if more than 24 hours have passed, since its last location was sent to Apple.

Have a look at the related articles:

If your Apple Watch is lost or stolen - Apple Support

Find your lost Apple device or AirTag with Find My - Apple Support

Did you know, that we also have a Japanese Apple Community?

Apple Support Communities - Japanese

As far as I know, if you put your watch in Lost Mode, other Apple devices can help to locate your device by using the Bluetooth connection, if Bluetooth has been enabled on the watch before you have lost it.