.... but not necessarily the right one.

First, phrenologists no longer exist. It is a defunct discipline. So you are going to have to deal with us...

My theories are:

1) did you spend significant time south of the Equator? Just like water flows counter-clockwise on the southern hemisphere, the hair also grows counter clockwise -- whereas in the northern hemisphere it grows clockwise. If you did do this, it is possible that this prompted a fluke in your scalp.

2) what is your ancestry? Some genetic groups have fine hair, while others tend to have thicker hair. Could it be that genetics made a booboo on that spot of your head with different kinds of hair growing at the same spot?