Can't Find Your Toolbox or Palettes?
If you've already checked your TAB key ( TAB toggles the toolbox and palettes on & off. Shift-Tab will hide all the palettes except for the Toolbox.) then you may of dragged the Toolbox below the screen area. Go to Edit>Preferences (the location depends on what version of Photoshop you have) and look for the button that says Reset Palettes and click it.