If he's emptied his Recycle Bin, he's hosed. He should open the Recycle Bin and see if the folder is still there and if so, restore it.
Unless you tell it to copy files to the iTunes Music folder, it will simply create links to the music files.
The better way to deal with this is to use the File|Add Folder to Library option, and then leave the folder where it is. Or, you can check "Copy files to iTunes Music folder when adding to library" to make iTunes make a copy.