Unlocking a Computer Locked by BitLocker

Log into https://myaccount.microsoft.com on another computer or phone
Click/tap on "Manage devices"
Click/tap on the name of the locked device
Click/tap on the "View BitLocker Keys" button
Look for the Key ID that matches the one shown on the locked computer
Click/tap on the "Show recovery key" button under the correct Key ID
Enter the shown recovery key on the locked computer
The BitLocker prompt screen on the locked computer can time out after an hour or so, so if the recovery key doesn't immediately work, restart the locked computer and try again.