Someone could--theoretically--mark all their posts as private whereby only their friends would see them. There were others who would pop in on occasion, post something (usually a pic), then delete it. Then there are the lurkers...
I think they probably have a troll or catfish account. I signed up for EP and never posted though so it might be an innocent teenager just living bi-curiously through the lives of us fckups. Like I was doing when I was a teenager on EP.