I have been having this problem for awhile and have been unable to figure it out.
I have a page that seems to not be linked the to space correctly. I can find the page via search and it appears to be under the Space it should be but it doesn't show under Pages. I even Move it under the Space in an attempt to make it visable but still it doesn't show. If I make it a child page by moving uner an existing page in the space it will show up.
There are no restrictions on the page.
Unsure if the following has anything to do with it but if I recall the page was created as follows. The content of the page was originally part of the Space content itself. As the project (space) matured I cut much of the Space content and pasted into a new page under the Space for historical purposes. I'm unsure if my troubles began at that point or some time later to be honest.