How do I make sure my blog is NOT found by search engines?That question is asked, regularly. And, in truth, there is only one truly effective answer.
Don't publish your blog on the Internet.This is similar to the question (and answer)
How do I keep my blog private?
Short of absolute effectiveness, the most obvious solution is the two Settings - Basic options. And there are other tweaks which you may find, in Google Webmaster Tools.
And, in the spirit of locking the barn after the horses have been stolen, there is the subject of Removing Your Blog From The Search Engines Caches. Search engine caches, like browser caches, won't clear overnight, if ever.
You'll need to note that the entries in "robots.txt", that result from the two Blogger options "Add your blog to our listings?" and "Let search engines find your blog?", are advisory only - not all search engines observe either setting. And the various search engines accept feeds from each other, in various relationships.