True scary story that happened to me

I was once at school when i was doing my work and suddenly out of no where a black hat appeared then in a second disappeared.I thought it was one of my tall friend.But when i looked over to see what it was i saw nothing.I got creeped out and told my friend.She told me that some ghosts want you to see them and some don't .When i heard that i was freaked out.But i think it was a GHOST.