I haven't found the corrrect fix yet, but if I type "lxpanel &" in a terminal emulator I get a working taskbar again. (logout doesn't work) You can also put a line "lxpanel &" in /etc/X11/xinit/xinitrc to make it more permanent.
From this you should have figured out that lxpanel is just a program that runs, what you have to do to start it is more an annoyance than anything.
I had been logged in via VNC (and installed tightvncserver remotely via ssh) and when I came back to the physical machine the taskbar was gone, so I started Googling. VNC maintains a set of preferences files which mostly parallel X(org) in ~/$HOME/.vnc/xstartup and it's possible something went in there by accident. The more normal config files are in ~/$HOME/.config/lxpanel and lxsession, then some system-wide ones in /etc/xdg/lxpanel and lxsession. But it's quite a maze, the lazy fix would be to experiment with replacing those files with ones from another machine. Just remember you can run lxpanel from multiple places if you get stuck. I can get to obconf just fine but I don't see anything in there that looks like a fix. You want a default set of config files. And you'll need to get out of X and back in, or reboot, to be sure you've cured it.
And BTW this is in 64 bit Debian Stretch on a Rock64, looks about the same as the Raspberry Pi I'm typing this on. And the same as LXDE in Wheezy on an amd64 machine, it's not at all peculiar to a Raspberry Pi.
When you're poking around in there (I used mc) look for files with recent dates. But maybe they got deleted too. I see changes in ~/$HOME/.config/lxpanel/LXDE/panels/panel and ~/$HOME/.config/lxpanel/default/panels/panel. I've replaced those 2 files with an original panel file from another arm64 machine. Now when it's booting I see the taskbar flash twice but then it goes away. Still a work in progress. Keep notes, one of the principle Lnux trade secrets.