Just finished reading the article of the above name in "The Best American Science and Nature Writing 2011". Written by Jill Sisson Quinn, it talks about the egg-laying mechanism of the Ichneumon wasp. The description of this procedure is interspersed with chunks of passages about why the author does not believe in the existence of God.
The title of the article refers to the fact that when the author was a little girl, she had written that phrase on a piece of paper and left it lying around. From time to time, she would pull out the paper to see if God did sign it. At different places, the author also cites an essay of Paul Bloom titled "In Science We Trust". According to Bloom's research, some things are hard-wired in the human brains, apparently from birth - things like the assumption that only an intelligent being can create order. Bloom's researches have also indicated that humans are born with the belief of an afterlife.
Well! It seems I have news for the author of "Sign Here If You Exist" It appears that God did sign - only, He signed on the human brain instead of the piece of paper the author left around