Open Question: How does facebook search work?

I know that someone had answered this type of question but mine is a little different. When you start typing in the search you get a drop down menu with a list of names or events or anything that starts with those letters, for names it can be either last name or first name. If you are not friends with a person I know that the drop down menu will order the people based on how many mutual friends you have. However, when I typed in a name the first person on that list was a person that I am neither friends with nor do I have any mutual friends, how did this happen?