Dear Maintainer,

I attached a 2nd monitor to my laptop,
and used lxrandr to set lxpanel to stick to the
laptop screen (screen '2', because it was on the right?).

After removing the monitor, and rebooting, the panel
was absent from the laptop screen.

Reattaching the monitor, I was able to reset the lxpanel
to 'both' monitors, then after detaching the monitor
again, the lxpanel was, as wanted, shown on the laptop
screen.

I suppose lxpanel might try and default this setting
appropriately, if detecting only one screen, you could ensure
lxpanel was visible on at least one remaining screen?

j