I can confirm that the Device Recovery solved the problem ... but it is a process that takes quite some time.
Depending on your device you might start at WP 8, 8.1 or vanilla WM 10 ... and it you still need to install all the updates in between.
Also WhatsApp backup doesn't always work as well. Mine could be restored, although I did have a backup on OneDrive. It was however the only way to get it all to work again, so it was worth it.
Word of advice:
Use a new Microsoft Account on your phone after you have recovered it, but before you install all the updates. Install ALL the updates, than do a Factory Reset on your phone. This will keep your OS version, but delete every App and account info. Now login with
your own account and use your backup.
Your WM 10 backups won't be fully compatible with WP 8 or WP 8.1 or older builds of WM 10. So first getting the latest build and than restoring your settings from backup is a good practice.