cp /usr/share/lxpanel/profile/Lubuntu/panels/panel ~/.config/lxpanel/Lubuntu/panels
lxpanelctl restart
Restaura no formato original.
Fonte desta dica: http://askubuntu.com/questions/64631/how-to-restore-the-default-lubuntu-panel
cp /usr/share/lxpanel/profile/Lubuntu/panels/panel ~/.config/lxpanel/Lubuntu/panels
lxpanelctl restart