If for any reason, you have lost information of any of your disks: either hard drives, memory cards or flash drives, you should try TestDisk & PhotoRec, a free, open source multi-platform application distributed under GNU Public License which is very efficient on retrieving data from those drives.
PhotoRec supports data recovery for the following filesystems:
* EXT2/EXT3 filesystem
You can download PhotoRec and TestDisk from HERE (packages available for: Windows (9x/NT/XP/2000/2003/Vista), Mac OSX, and Linux).
Ubuntu users just have to run the following command in a terminal:
sudo apt-get install testdisk
The, to run it (still in a terminal):
PhotoRec works with HardDisks, Cdrom, memory card (Compact Flash, Memory Stick, SecureDigital/SD, SmartMedia, Microdrive, MMC...), USB Memory Drives, DD raw image, EnCase E01 image, and also various portable media players including iPod and various digital cameras.