Here's the beauty of digital indexes: it's so much easier to find things you may miss in a paper or microfilm index. The relevant results are right before your eyes. And this may give a name new life under the eyes of a different transcriber.
While running a few names through the Missouri Birth Records, 1805-1980 database, I came across Augustin LANKAU. Guess what? I never came across this child when I looked at these records years ago at the City Library, nor in any searches of Catholic church records. I knew there was a gap or four years between births in this family, but no more. Now I need to find out what happened to this boy. He did not live to 1900.