Store Apple Watch Data before unpairing with stolen phone

Hi

I'm afraid that it will not be possible to retain any Activity data since the most recent data, if any, that was:

• Synced automatically from the Apple Watch to the old iPhone.
• Then subsequently backed up from the iPhone as part of an encrypted iPhone backup (iCloud backups are encrypted as standard).
• Then restored to the replacement iPhone:
  • Locate backups of your iPhone, iPad, and iPod touch - Apple Support
  • Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

In order to pair the Apple Watch to the replacement iPhone, your wife will first need to manually erase the Apple Watch by following these steps:

On the Apple Watch, go to: Home screen (via a single press on the Digital Crown) > Settings (cog icon) > General > Reset > Erase all Content and Settings.

Then pair it to her new iPhone via the standard process, choosing to Restore from Backup, if offered the option:

Set up your Apple Watch - Apple Support

According to the "If you don't have your old iPhone or a backup" section in:

Switch your Apple Watch to a new iPhone - Apple Support

You should erase your Apple Watch, then pair it with your new iPhone. If you’re asked to restore from a watch backup, select the most recent backup. You will lose Activity, Workouts, or settings on your watch that changed between the last backup and now.

Without an iPhone backup, you’ll need to set up your Apple Watch as new. You will lose any previous Activity, Workouts, or settings, but your other content will sync from the new iPhone to your Apple Watch.

To be clear, as it says in:

Back up your Apple Watch - Apple Support

Apple Watch content backs up automatically to your companion iPhone, so you can restore your Apple Watch from a backup. When you back up your iPhone to iCloud or iTunes, your iPhone backup will also include your Apple Watch data.

So, if you restore your new iPhone from a backup you made, your workouts, achievements, etc.should also be restored to your watch.