A blog seemed to have somehow added itself to my list of blogs, and I would get updates from there in my feed, but the blog would not appear in the list of blogs I was following, for me to unfollow it. I looked for help over the web, but everyone had the usual tips and they did not help. I visited the blog, and it seemed to have only three to four posts, beginning in January this year. It was viewed more than eight thousand times, and did not show any followers. I found a profile leading to google circles. It had no friends and was probably designed by someone for mysterious reasons. All I wanted was to unfollow the blog, so I did not have to see the updates in my feed. I blocked the google account of the owner of that blog, and guess what? I stopped getting the unwanted updates on my blog too. I hope it stays that way.
For all those unwanted blogs that you want to unfollow, and they do not show in "Manage Blogs I'm Following", yet, appear in your blog feed; go to the google link of the blogger and block it. If you still get updates, let me know ! We'll figure it out. :)