Switched phones? No worries!
Your KEEP is linked to your account, not your phone.
Just download the KEEP app (via the App Store or Google Play Store) on your new phone, sign in with your account, and voila! You're back in control of your KEEP.
It's as simple as that!
If you run into any difficulty, try forgetting your KEEP from the Bluetooth menu of your old phone and trying again with your new phone :)