It's just a sensationalist attention grabbing headline and nothing more. Even if the conclusions from the data were true - that 38% of agnostics were believers - it still doesn't get you anywhere near "atheist might not exist". However, the far larger crime is that this article is blatantly committing the fallacy of false equivocation. An "atheist" is someone who lacks a belief in God. You can be an atheist and still be "spiritual". You can be an atheist and still believe in predetermination. You can be an atheist and still believe in the supernatural. None of these are exclusive propositions to atheism.
In regards to "INTERNAL MONOLOGUES" they author is merely describing decoupled cognition. This has nothing to do with a belief in God or in the supernatural. It's a process of meta awareness that allows us to bounce our ideas off of an imagined third party. Most of the time people imagine what dad or mom would say or someone whose opinion they respect.
As for "EVOLUTIONARY PURPOSES" Sam Harris has written on this extensively about the importance of ritual and special words for special occasions:
https://www.youtube.com/watch?v=zLKNvBdUtZY
I think mostly what is happening with this article is they are addressing the "nones" (people who don't belong to a religion) as though they are agnostics. This simple isn't the case. The majority of nones have a belief in God. It truly is just a poorly written article all the way around.
Here's a much more informed article upon the topic: http://www.religionnews.com/2014/03/13/none-atheist-christian-evangelical-pew/