You can try and repair the flash drive, just right click on the drive letter for the drive, such as, if it is "D" drive right click select properties. The second tab says tools on it open that tab select "check now". I have also used the back up now at the bottom of the page to recover files, but it is usually better to use the back up now to create a director for your files and sync them when you attach the flash drive.
If this does not work I would download Super FDisk is is a Linux based disk that usually comes in a ISO format. So you will need to burn it to a cd rom leave the disk in your CD/DVD drive, make sure the flash drive you are having problems with is attached directly to the computer ( you can use a usb hub but sometimes the device is not found) so Super FDisk can find the device. Yes you can use thus method for hard drives as well.
Super FDisk should mount the flash drive for you then you can recover your files. There are lots of tutorials on how to use Super FDisk so I'm not going to give a blow by blow accounting of what you need to do. Simple do a search on your preferred search engine.
Best of luck