No widget menu under Appearance

I’m running on WordPress 4.2.2 and cannot see the Widgets menu under “Appearance” when using the Pinboard theme. The theme is obviously widgetized already and the issue must be theme-related because the menu appears when any other theme is in use. I eliminated the obvious causes, e.g. Deactivated all plugins, reset all theme options, even reinstalled WordPress core. I have been fiddling with the functions.php & sidebar files thinking there may be a wrong reference, but no luck so far. Any suggestions would be greatly appreciated!