I'm not very far from this idea somehow.
I don't believe in "God" if it has to mean "Creator", "First Cause", "Provider" or "Great Architect" (and according to the dictionary it has to, or it is not "God"). I would reject the theistic or deistic "God" alike.
Yet I am fascinated by prayer. People prayed to the gods, spirits, "demons" (a positive word in classical Greek) long before the idea of "God" (capitals intended) came up. According to some Ancient Near East scholars, in addition to the national or natural gods and goddesses there was a sort of "personal god" to each individual, family or clan. When Israel shifted from polytheism to monotheism the prayers did not change. Monotheistic Christian believers today can easily pray the Psalms, although some of them come right from the polytheistic period. Even now people who don't believe in God anymore still pray sometimes -- I do.
Whom are we addressing in prayer? Nobody really, but we still do. We have to posit "someone" listening when nobody listens. That's exactly what I understand in Matthew's statement "pray to your Father who is in secret". We have to posit "someone" winking to us when we take fortuitous events as personal "signs" -- as we all do sometimes. We have to posit "someone" speaking when we address ourselves in the second person. This non-being is, I guess, an essential "spot" in our symbolical structure.
In the middle ages there was a minority current among theologians (Meister Eckhart being probably the most famous) according to which everything that could be said about God (including his "essence" or "existence") was radically inadequate: it is known as "negative" or "apophatic" theology. This current can be related to ancient Gnostic views (in which the true God was not the Creator) as well as Eastern philosophies (Buddhism, for instance). It was close to atheism really, albeit with a spiritual dimension which most post-Christian atheism misses.
The impossibility of knowing the "god" of prayer, together with the certainty of being known by "him", is beautifully expressed in Psalm 139:
O LORD, you have searched me and known me.
You know when I sit down and when I rise up;
you discern my thoughts from far away.
You search out my path and my lying down,
and are acquainted with all my ways.
Even before a word is on my tongue,
O LORD, you know it completely.
You hem me in, behind and before,
and lay your hand upon me.
Such knowledge is too wonderful for me;
it is so high that I cannot attain it.
Where can I go from your spirit?
Or where can I flee from your presence?
If I ascend to heaven, you are there;
if I make my bed in Sheol, you are there.
If I take the wings of the morning
and settle at the farthest limits of the sea,
even there your hand shall lead me,
and your right hand shall hold me fast.
If I say, "Surely the darkness shall cover me,
and the light around me become night,"
even the darkness is not dark to you;
the night is as bright as the day,
for darkness is as light to you.
For it was you who formed my inward parts;
you knit me together in my mother's womb.
I praise you, for I am fearfully and wonderfully made.
Wonderful are your works;
that I know very well.
My frame was not hidden from you,
when I was being made in secret,
intricately woven in the depths of the earth.
Your eyes beheld my unformed substance.
In your book were written
all the days that were formed for me,
when none of them as yet existed.
How weighty to me are your thoughts, O God!
How vast is the sum of them!
I try to count them--they are more than the sand;
I come to the end--I am still with you.
