What bitlocker id key? is it not the recovery key? If you don't have the password and recovery key, there is no bitlocker recover if you connect it to a Microsoft account read
As the recovery problem, it depend what data that user lost ,for data lost , the data recovery tool can restore lost data back , and for password lost , if it is Windows password , maybe you can ask Windows password recovery tool for help,
bitlocker encrypted the data, if you can't decryted it first, there is no data to recover.