Several methods, but whenever one of the Palettes display isn't on screen anymore open the CUI editor, select the current Workspace, pick the [Customize Workspace] button on the right, expand Palettes, select Command Line or whichever Palette is missing and change it's Orientation to something else like Bottom.
As long as your Workspace Settings… When Switching Workspaces is set to: "Do not save changes to workspace" simply switching to another Workspace and back again will fix the Palette as long as it's not set to Floating in the Workspace.