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?
First, press
Alt+F2. This will bring up the Run program dialog box.To recover the panels, type in
xfce4-panel and click Run.To recover the desktop, type in
xfdesktop and click Run.