Why can't I see my collaborator's draft page?

Total beginner's question here, but my collaborator (the site owner) created a not-linked page yesterday, not enabled, and I can't see it in the page list. But he can see another no-linked unenabled page that I created - I can't work out what the difference is. 

Any ideas? I need to edit his page! 

Thanks, Jenny

The site owner can of course see everything.

I suspect your permission level is not high enough to see what the site owner created.