We always encounter such a problem that a USB flash drive corrupt with much important data in it, after fix the external hard disk up the data always have been formatted.

If you want to recover lost data from the formatted USB disk,  well, you must avoid adding any new files into the disk before you getting files back, because the new data will take up the old, formatting is only removing the information of the data, your original files will still be there. The original files will be unprotected by the ToC (Table of Contents) and are ready to being written over.

Make sure you don't deal with the USB hard disk, then you can ask a Data Recovery software for help, Disk Doctors Photo Recovery (Mac) is a good alternative.  Free download

Disk Doctors Photo Recovery is a perfect removable media recovery software that designed to recover missing, deleted and formatted files on digital cameras, mobile phones,  mp3/MP4 players, iPod series and other devices that with USB/Firewire port via a Mac OS computer.

In addition, it supports scanning digital photo, audio or video files on your USB hard drive  in a specific media format, like PSD, RAW, JPG, PNG, MP3, WMA, MP4, MOV, VOB, FLV, etc.

Thanks to its easy to use interface, it can be used by first time users with ease. Here is a feature table for ready reference:

Supported Memory Card Standards: CompactFlash, Memory Stick Duo, Memory Stick Pro, Memory Stick Pro Duo, SD Card, mini-SD, micro-SD, MultiMediaCard MMC, SmartMedia, XD Picture Card, etc.

Removable media: IDE/ATA/STAT/SCSI hard drives, USB flash drive, Firewire hard disk, ZIP external drives, iPod, MP3/MP4 players, etc.

Supported File Formats: Images: JPG, BMP, PNG, TIFF, GIF, PSD;
Video: MPG, MPEG, AVI, MOV, MP4, M4V, 3GP, 3G2, RM;
Audio: MP3, WAV, MID, MIDI, M4A, M4B, AIF, AIFF, AIFC, AMR, RA.

Note: Disk Doctors Photo Recovery software must be installed on Mac OS X 10.4.11 and above, which includes leopard.