Someone messed with my timeline

When I was in high school, there were four Catherines in my class. Well, three actual Catherines, and one Kathryn. Near enough.

I can remember the last names of three of them: Kathryn L, Catherine C and Catherine Also-C. I can't for the life of me remember the last name of Catherine #4.

My theory: someone went back in time and erased her from my timeline. Nothing else has changed; they just deleted one Catherine. I asked my Mom, and she said there were only ever three Catherines in my class. Her timeline never had Catherine #4 in it.

But there were four. I know there were four. I just can't prove it because we didn't have a yearbook (being British).