$ mate-panel --help
Application Options:
--replace Replace a currently running panel
--reset Reset the panel configuration to default
Your first choice option is mate-panel --replace, because the --reset option will reset your panel customizations (like panel placement, applets, launchers, etc.).
By default, you should be able to open a terminal with Ctrl + Alt + T if you need a terminal to replace the panel.
In addition to the command for replacing the panel given above, you can also open MATE Tweak and switch away from, and then back to, your layout (if you have saved a custom layout). In the terminal, run mate-tweak to bring the app up.