This is something I've always noticed happening to me. The basic principle is that as soon as I notice something interesting, it immediately disappears. It would not have disappeared had I not noticed it. Here is an example scenario, from which I derived the name of this theory:
I'm riding in someone's car, and out of the corner of my eye I see a sign that I want to read. It probably has something really funny written on it. I turn my head to look at it, but no sooner have I done this than an eighteen wheeler comes from out of nowhere and obstructs my view of the sign. The eighteen wheeler stays with our vehicle until just after the sign is out of view. If I had not seen the sign, the eighteen wheeler would have stayed where it was. It appeared for the sole purpose of obstructing my view. I don't believe the driver of the truck does this on purpose, but there are definitely some cosmic forces at work here.
This happens to me all the time, and it's been happening for as long as I can remember. Last week, I got some concrete evidence of this phenomena.
When I take the 128 bus to West Seattle, there is a place on the route where the bus goes down a high hill overlooking Puget Sound and several islands. The view is breathtaking. One day last week I happened to be sitting in the very front row of the bus, and I happened to have my camera with me. I decided to film our descent. Here's what happened:
This is exactly what I'm talking about. Bah!
If you've got any similar experiences you could share, please email them to me.