Yeah I'm guessing because you didn't let the process finish and rebooted, it just vanished.
You have 2 possible options. Either specialized software to undelete files... or if that doesn't work.... have the drive sent out to a computer forensics company if you need it that badly. And for any reasonable chance of a full file recovery, the data blocks that hold the actual contents of any of the file must not have been overwritten since deletion. So you would need to stop using the drive now in order to increase the chances that the actual file data is still intact and doesn't get overwritten. The other outcome can be that forensics might only provide you with a partial file recovery.
Sometimes forensics can recover a full file that has been partially overwritten, but it's very hard to do. An overwrite can leave a weak "ghost like" residual of the original data (on blocks that are positioned laterally to the sides of the original block for example) that can be recovered and pieced back together.
It is similar in concept to a magnetic cassette tape with a song that's been recorded over a 2nd time with a new song and the original song can still be heard faintly in the background... especially during quiet passages of the new recording. That's either due to a poor erase head or lack of one... or... it is echoes of the original song that bled out into the magnetic material on either side of the main track channel that the playback tape head can still faintly pick up.
That's why special delete software (like "Eraser") was designed to delete the data by overwriting the same blocks multiple times with random data so forensics have a hard or even impossible chance of recovering that ghost data.
Otherwise as Hack said....you are SOL.
