You mean, you know people who you know to have been exposed to the person who was infected? Are you certain that they were in the same building at the same time? If not it's not really a defeater to my hypothesis. If your friends were not exposed to the infected individual they would not have been notified.

Admittedly the scenario I'm proposing seems unlikely. Seems they would have at least mentioned it if they were going to tell the folks who might have had contact with the individual. However. I'm leery of jumping to conclusions.