Thanks for the vote of confidence, but without really digging in to the code, I'm not sure how Google got to see your logged in page. (And it's possible even digging in to the code we wouldn't be able to figure it out.)
I mean, I'm thinking it would likely have to do with how the data is coded in the page, and how it's secured. The Googlebot is pretty aggressive -- I've known it to try to submit site search forms, for instance -- so I think if there's any way to access the "logged in" page code without actually having a login ID and password, Googlebot will eventually find it and try to get to it.
Is it important for this page to be indexed? If not, you could add it to the Disallow list on your robots.txt. That should keep Googlebot away, but it would mean the page would eventually drop out of Google's index.
Generally speaking, though, as long as you're certain your human visitors can't see or access the "logged-in" content when they're in "logged-out" status, I wouldn't worry too much about it.