Version: (using KDE KDE 3.1)
Installed from: SuSE RPMs
The window is hidden by double clicking on the title bar.
If the mouse is moved off then placed on the title bar the window unhides itself and isn't shown as a window on the desktop panel on kicker (this possibly may be intentional).
However if the now unhidden window is kept unhidden by double clicking on the title bar (thus returning to the initial state), the window isn't shown on the desktop panel.
That one is a kwin (or kwinmodule) bug. Reassigned.