I have this issue as well. I have 1,750 people in my tree and finding any particular one is a trial using the Find button. I have a dozen people with any given common family first name, and since it sorts by last name but you have to look them up by first name, they do not appear all in a row together. It is extremely frustrating.
My work-around is to export it to CSV and search in Excel. Very inconvenient. :(