As I was experimenting with panel sets and layouts, I inadvertently hid a panel. Help!
Don't panic. You can easily restore panels. Here are several options:
Manually go to the Window menu and select a panel you want to display.
Use the appropriate keyboard shortcut to display a given panel.
If all panels suddenly disappear, you've probably accidentally pressed F4. Press it again, and your panels should reappear.
You can always restore the default panel set by choosing Window, Panel Sets, Default Layout.