There is no real solution once you start encrypting the drive. You are pretty much lost.
That is why they always advocate to make a backup of the drive before starting, and to ensure that you are going to have uninterrupted power (as in an uninterruptible power supply, aka battery backup) when engaging n the use of encryption and decryption tools for hardware.
Sorry you had to lose you data - next time, though, make the backup like you're supposed to.