BitLocker keys get backed up automatically to the Microsoft account used to set up the device. You need to:
On another computer or phone browser, go to:
https://account.microsoft.com/devices/recoverykey
Sign in with the same Microsoft account that was originally used on the Surface when it was set up or last used. It might still exist in Microsoft’s system as an account.
If there was a linked phone number or alternate recovery email, try Microsoft’s account recovery options first to regain access.
Microsoft won’t look up or restore it from purchase info.
There is no legitimate way to bypass BitLocker encryption without the recovery key.
If the key isn’t in any Microsoft account and you have no print-out or USB backup, the only technical option left is to reset or reinstall Windows. That will erase everything on the drive, including all data and settings.
See: