Isn't this just a coincidence?
There are two possible explanations:
1. All the Muslims that missed work and school did so by coincidence.
2. Some missed work because there was a general warning sent through out the Muslim community that there would be an attack on 9-11.
The news accounts above support the latter. A statistical analysis of the unplanned absences of Muslims working around the World Trade Center would establish if all the absences were coincidence or not. I will never know one way or the other about my wife's co-worker.