Unable to find my old device under my account

If the laptop no longer appears in the Devices list, the BitLocker recovery key can still be available separately.

Try these locations:

1. On another device, open the BitLocker recovery key page for a personal Microsoft account: https://account.microsoft.com/devices/recoverykey
2. Sign in with the Microsoft account that was used when the first laptop was originally set up.
3. Compare the recovery key ID shown on the locked laptop with the key ID listed in the account, then use the matching 48-digit key.
4. If the laptop was ever signed in with a work or school account, check https://aka.ms/aadrecoverykey, then go to Devices > the device > View BitLocker Keys.
5. Check whether the key was saved elsewhere when BitLocker was enabled:
   • a printed copy
   • a USB flash drive containing the saved key file
   • another Microsoft account that may have been used on that laptop

Important facts:

• Microsoft Support cannot retrieve, provide, or recreate a lost BitLocker recovery key.
• In some cases, a device may be missing from the Microsoft account device list, but the recovery key may still exist on the recovery key page.
• If the device was set up by someone else, the recovery key might be stored in that person’s Microsoft account.

If the recovery key cannot be found in any of those places, the remaining option is to reset the device using Windows recovery options. Warning: resetting removes all files.

References:

• Find your BitLocker recovery key
• BitLocker overview
• unable to retrieve my bitlocker keys - Microsoft Q&A My microsoft account is not showing Devices so i'm unable to retrieve my bitlocker keys.
• Missing Devices - Microsoft Q&A My Computer Is "NOT" shown on the Devices Tab in my Microsoft Account Page.
• How to find bitlocker recovery key when there is No 'BitLocker recovery key found for this device.' - Microsoft Q&A