I have been using a usb drive 512mb and I unmounted it lastnight and now one folder on there has lost its contents and if I go to drag anything into the folder I get an IO read/write error.

Is there a way to check the drive to see if it is faulty?
And possibily recover or repair the files that are not apparently there anymore?

I have got the permissions set so that reading and writing is set and allowed.
Any other folder in the drive is able to be accessed and files dragged into it.