Click on the orb, type switch between windows in search index bar. It should be at the top in the list, click on it and it should open up and reappear in your quick launch bar. If it doesn't reset it self in quick launch bar, follow instructions above, then right click and click send to, create a desk top icon, then drag new desk top icon to quick launch bar. That should do it for yeah.
The next thing I can offer is a system restore to an earlier date to see it that will correct the problem for you. Other than that, looks like a reinstall of OS might be in order. Though your problem is very odd, I'm guessing the answer is something simple and we are just overlooking it. What? is the question. I'll keep searching.