I was born with a bald spot on the side of my head. About the age of 14 I noticed that some hair in the middle of the bald spot grew and is long. Now at age 23 it’s still there and some strands of hair if you look closely here and there. What caused this and why did some hair grew back.
I don’t have a clue without seeing just what you are talking about. I’ve gotten similar questions in the past, and the only thing I could think might’ve been the cause is a birthmark or some kind of trauma. As to why some hair grew in… again, I’d have no clue. Not everything can be explained (and I’m even more limited because this is the Internet and I’ve never seen you).
There are some areas where there are typical inherited patterns and others that are not typical. For those that are typical, we might be able to tell you more about the cause.