Crashed when creating a partition - now missing drive space!

In fact there isn't any space free on your disk in the sense of unallocated disk space. But you probably resized the Logical Volume Macintosh HD (disk1) residing in the Logical Volume Group Macintosh HD (disk0s2).

To expand the Logical Volume Macintosh HD to the full available size you have to use an undocumented command: diskutil cs resizeVolume UUID size.

1. Boot to your Recovery HD by pressing cmdR while booting.
2. Open in the menubar Utilities->Terminal
3. Enter diskutil cs list to get a list of all CoreStorage items.
4. Enter diskutil cs unlockVolume LVUUID (LVUUID is the UUID of the Logical Volume, usually it's the last UUID in the list you got earlier) to unlock the encrypted Logical Volume Macintosh HD. You have to enter the FileVault passphrase now.
5. Enter diskutil cs resizeVolume LVUUID 0g (0g is a magical number here - it will expand the Logical Volume to the whole available size of the LVG).
6. Enter exit and quit Terminal
7. Reboot to your main volume