Recover accidentally reformatted encrypted HFS+ volume
In this case you should recover the disk contents from backups.
The format command will have overwritten (small) parts of the disk, so in order to get everything back, you'll want to recover from backups.
If you haven't got backups, you will need to try changing the partition table to indicate it is a CoreStorage volume and then attempt to manually edit enough of the partition to ensure that it can be mounted (if possible at all). As the partition was encrypted, this will probably prove to be very difficult, if possible at all.