Disagree. There's no faith involved whatsoever in an atheistic belief of that sort. If there's no evidence for something being true, your default position is that it isn't false? What if I were to say there's a giant inflatable pink rhino floating behind your head right now (I'm assuming there's not...), would your default stance on that rhino's existence be agnostic one as there's no evidence that it doesn't exist? I don't say that there is no God, but given that there's no evidence to suggest there is, why would I believe there is?
It's impossible to prove the non-existence of something anyway, regardless of whether God is mentioned in the question. Because of this reality, the burden of proof must always lie with the believer.
Also, yes, I do believe that the default position is non-existence in the absence of evidence.
In the absence of reliable, valid testing processes for the hypothesis, and clearly defined evidential requirements, my argument is that the hypothesis is untested and therefore it's status is unknown, and until the effect, and therefore evidence, can be established, it is also irrelevant.
To use your example, until I turn my head and check, the status is unknown, and unless it's about to hit me in the back of the head, it is also irrelevant. Alas, such an example is not a good one to use, because you've given an example of an easily testable hypothesis.
I prefer to use Russell's teapot, and again, the idea is similar. It is not that I believe in the teapot, however I do not assert that the teapot is probably not there either, because both of those positions are a leap of faith. The only position that makes sense is that you don't know. But again, it is also irrelevant whether it is there or not if it cannot be detected...
You are right that it is almost impossible to prove non-existence, however for most things, it is possible to define the evidence that should be there in such a way that absence of evidence is a good equivalent to evidence of absence. The problem is that this does not extend to the idea of a god.
The very idea that absence of evidence is evidence of absence when applied to the god hypothesis can therefore be nothing more than an act of faith, because there is no logical reason to accept it to be true. Even when applied correctly, it is still an assumption, hence the entire line of reasoning is an example of argumentum ad ignorantiam and hence fallacious.
Incidentally, what is the problem with having faith or belief in assumptions? It is a cornerstone of the scientific method after all that some aspects are taken a priori, as unless you do, the whole process falls down...
Along with Russell's teapot (which stands for an infinite number of undisprovable entities), the Flying Spaghetti Monster is another great example to illustrate the point. The point of said example is that, like the Abrahamic God, the Spaghetti Monster is undisprovable, however, I'm yet to meet a person that believes the hypothesis of their existence is on an even footing with the hypothesis of their non-existence.