When a player enters the game after scene 1, s/he should get a clear notification that this is not scene 1 and get a link to scene 1, so that they can immediately start to read up on past events. Even so on the top of the side the current scene-number is mentioned it is not enough. From the handful of people I know personally who play Storium, two (incl. me) started a game in scene 2 or 3 of chapter 1 and we both didn't notice until much later that we didn't start in the first scene.