Not to burst anyone's bubble, but the presence of dark matter in the universe IS observable. In fact, it's the observations that led scientists to conclude that there is such a thing as dark matter. To put it simply, we can calculate how much matter there is in a given galaxy by adding up the amount of observable matter (basically, stars), and we can calculate the rate of rotation of each galaxy. The problem is that the rate of rotation and the amount of matter are related to each other by some very basic laws of physics, but the observations of matter and rotation do not add up, no matter where you look. Which is why people suspect that there is some other large quantity of matter in each galaxy that is affecting the rate of rotation but otherwise is not part of the galaxy's stars, hence dark matter.

In other words, the mystery is really limited what dark matter actually is. And there wouldn't be much of a mystery there either if we had practical ways to travel interstellar distances, but right now, basically the only way that we know what something outside our solar system is composed of is by observing its radiation, and there is apparently no radiation from dark matter (that's the dark part) so we just don't know what it is.

Now, if you want to talk about a physical phenomenon that is analogous to God, maybe you should stick to dark energy, but I digress . . . !