Hi,
Unfortuantely, there isn't anything that can be done. The HDD has been formatted, and there is the complication of the bitlocker encryption not fully decrypting, so there is an infinatesamly small chance of ever recovering those files
You could try accessing the HDD using a Linux distribution to try and at least access the drive, but I do not hold out any hope of data recovery..........
Regards,
Golden