Apparently, this happens whenever you exit from Xubuntu without logging off properly, e.g., pressing the reboot switch on your computer. Thankfully, fixing it is quite easy.
So how do you solve the problem of Xubuntu's disappearing desktop? Or the disappearing panel?
Alt+F2. This will bring up the
Run programdialog box.
To recover the panels, type in
To recover the desktop, type in