Zombies on Five?

So, my previous highest round on "Five" was round 15 (I'm always stuck with people who aren't that good at "Five"). Last night, I got to round 23 and we would have gone much further but we didn't because the host ended the game. Anyway, on the leaderboard, it still says my highest round is 15. Why didn't round 23 record as my highest round? Is it because the host ended the game? This is really frustrating, as my friends have never got that high on "Five" before (They blame the "poor construction" of the map for they're low level rounds on "Five".) I just really want to prove to my friends I'm the best at "Five" out of me and them, haha.