If khelpcenter is called (for example: help button from Klipper configuration page) and the requested doc cannot be found, it displays the generic "Documentation not Found" page.  However, as it does not display the name of the page actually requested, it is hard to distinguish truly missing docs from cases where the wrong doc is being requested.  For example, in the Klipper case, the help button is likely requesting help:/kcontrol(5)/klipper intead of help:/klipper, which actually exists.