Even if theism is a failure, it's still superior to atheism

[R00tKiT]

But there are times when absence of evidence *is* evidence of absence. For example, if I fail to detect an adult african elephant in my room, I can conclude that there is no adult african elephant in my room. 

Nope, you can't, if you fail to detect elephants in your room, this just means you failed to detect them, nothing more. I mean, most accidents in life happen because people are hilariously bad at detecting things.......?

Besides, I can say the same thing about quarks, or electrons : I fail to detect any trace of quarks or electrons in my room, they have no distinguishable form, or smell, or color, or flavor, they're undetectable even if one uses the most sophisticated microscope available, and science tells us they're extremely small, very suspicious.... So I conclude there are no electrons and quarks in my room..

I'll anticipate one possible objection : you may say there are experiments that can be done to show electrons are real, but this is irrelevant in this context. You're telling us that you, personally -not experiments, or machines, or other people-, couldn't detect an elephant, and from that fact alone, you allowed yourself to come to the hasty conclusion that the elephant doesn't exist. This is obviously a mistake.

But going deeper, if the detection is impossible even in principle, what does it even mean to say that something exists? I could then equally well argue that undetectable unicorns exist in my room. Who is to say otherwise?

If you provide plausible reasons for the unicorns existence -aside from detection-, then we have to assess these reasons on their own merits.
Some centuries ago, most discoveries in modern physics were completely undetectable, even in principle........