There are a limited amount of characters in each world as you play?

Just double checking that I am not crazy since I am a relatively new player but still have a lot of unlocked characters. I started having it where I can't find everyone. Usually Elsa I have the hardest time finding when I am looking for her. So I think it's set up where each hour you play or so the characters on the map are limited? Or am I wrong and I have a glitch?