Hi Sonny,
There was a bug (in version 2.3.8.1 I think) where when page permissions were saved it as not correctly updating the checkbox for all users in the UI. So the problem was if you didn't notice that All Users was unchecked and you saved the page settings again it would lose that setting.
That is my best guess of what happened, I don't think it was hacking or any kind of security bug. Sorry for the inconvenience.
We don't have any comprehensive audit trail for changes to settings. For the next release I will make it log it to the mojoPortal log as INFO when someone changes the view/edit roles of a page or module.
Best,
Joe