If you deleted the file using KDE, it will probably be in your trash folder on your desktop. If you deleted it from the command-line then you won't be able to restore it.
You may be able to find it (or bits of it) if you can remember some of the text that the file contains. In an xterm, run
(or whichever partition it was on), press backslash (\) and type in some text. Press Enter and it will start searching for that on the disk itself. You can then select the text in the xterm to copy it, and middle-click to paste it into another window, and get (at least bits of) the file back that way.
Hope that helps,
— Robert J. Lee