The first step for pen drive recovery on your Mac is to download Disk Drill Basic. This app is completely free and will allow you to start the process of flash drive recovery on your Mac OS X. Simply download the installer and follow the instructions.
Use awesome possibilities offered by Disk Drill to ensure the safety of your files. Recovery Vault and Guaranteed Recovery options let you save your files before something is even merely happening. You'll never need to run Mac file recovery from a flash drive again! Recovery Vault creates a special map for Disk Drill to locate lost files and Guaranteed Recovery creates invisible file copies when files are moved to Trash. Such files will be recovered right away when needed.
Even when you think the situation with the lost files is hopeless Disk Drill will still try to save the day. It offers Deep Scan that digs into core file structure and looks for file signatures that are still there somewhere and collects the pieces to restore the files. The more known file signatures are found the easier it gets to recover files of various types including XLS, DOC, AVI, MP4, JPG.