Here is a summary about mold from the CDC: "Summary
In summary, Stachybotrys chartarum (Stachybotrys atra) and other molds may cause health symptoms that are nonspecific. At present there is no test that proves an association between Stachybotrys chartarum (Stachybotrys atra) and particular health symptoms. Individuals with persistent symptoms should see their physician. However, if Stachybotrys chartarum (Stachybotrys atra) or other molds are found in a building, prudent practice recommends that they be removed."
Unless you were taking down walls and/or ceilings..you did not see black mold.
I have seen black mold. It was between layers of wall board in a bathroom. For many years the previous owners just put up another layer of wall rather than do a real job of renovating (that bathroom was 6" wider when I torn out all the wall board that was just put up one on top of the previous).
I know that mold can look black... but..it is really a very very dark green.