God is just like a wind. Why ? We didn't see the wind but the wind still exist because we fell it. Just like god we didn't see god but we feel that there's a god.
You have very interesting logic and somewhere even there is a rational grain. After all, we really do not see the wind, but we know about its strength, and of course we see the consequences of manifesting its strength. Perhaps so with God. We know about its existence and see its manifestations.