Re: What happened in your sims 3 game today?
Hey, you said Chang's world is Riverview. There was an issue with cc and store-bought content uninstalling itself because of the EA App, and Riverview is a downloaded world that didn't come with the base game or its expansions. They patched this issue but maybe you haven't got that patch or I don't know. I had the same thing happen to me with saves that were in Monte Vista, Lucky Palms, Riverview because the world my save was in, didn't exist.
To check if that is the issue, then when you launch Jarrod and Margo's game, which is still ok (is that one in Sunset Valley which came with the game?), then when you get to the lobby, where your family or lot portrait appears (and then you normally click on that to choose them and load that save), try clicking on "+" create a new game instead, and then when it gets you to choose a world to play it in, look at the drop-down menu to see if Riverview, or any other downloaded world, is listed. If its not listed, then that is what the problem is.
If that is the problem, then find the EA App launcher patch or click on the 'repair' or 'update' feature of the app, and then I'm not sure if you still have to re-download the items or just reinstall them. Try both. I haven't had to do it again since the patch.