Which version of eZ publish do you use? If you are able to reproduce this problem on your version, please write step-by-step instructions and report it in our bug system.
I did a manual install, and probably this setting is normally set by the install wizard, which I didn't use. I added it manually, and now it works as expected.
This page might be useful for future manual eZ publish configuration. http://ez.no/doc/ez_publish/technical_manual/3_6/installation/manual_installation/manual_configuration_of_ez_publish
Check "The admin siteaccess" part and compare it with your admin settings.
I think the bug may need to be re-opened as I am having the same problem with ezPublish 4.0.
Already checked my admin site access has ShowHiddenNodes=True
Public site access has ShowHiddenNodes=False as does the main site.ini file
According to my understanding of the manual and settings files, this should enable me, as the administrator, to hide nodes from the public but still view them in the admin interface. Unfortunately it doesn't and the only way I can get my nodes to become visible again is to run the SQL query posted above.
I have cleared all caches as well just in case there was a setting causing interference but to no avail.