If a file on a network drive is deleted or overwritten, it can be restored as long as the files have not been irrevocably removed. (cf. emptying the Recycle Bin under Windows).
To restore a file, right-click in Windows Explorer on the directory where you want to restore the data. Then select the "Restore files..." item in the context menu that appears. You will get a selection of files that can be restored. Select the appropriate file and click on "Retrieve file". If this file already exists, you must specify a new file name.