It sounds like the server caching program threw you a cached page from the system that someone else received. It doesn't mean you are logged into anyone's account, it's just a glitch that does that every now and then.
Spunky, at a glance I don't see any deleted posts attached to your account other than the two you deleted a few days ago. You can locate all of your posts if you click your username then use the drop menu to select to view your posts. I hope that helps