In gameplay, I tried to edit a sim's appearance via Nrass/Master Controller and while I was able to do so- the game glitched out, and all of the CAS options' icons (the ones you click to make your sim) glitched into the game and then disappeared. Suddenly, the whole world and every sim in it disappeared. I tried to save the game and restart but it still looked like this:



What happened and what can I do to fix this? I still want to play my family but I can't seem to see any of them.

I'm not sure what happened, or quite what's going on in your screenshot. There may be a way to fix this save, but it could take some experimenting. Or you could revert to a previous version of the save, which shouldn't be affected. Even if you've never made one, the game keeps the data from the second to last time you saved.

Open Documents\Electronic Arts\The Sims 3\Saves, and you'll see a folder with your save name and another with the same name plus a .backup extension. So if your save is SunsetValley, you'll have a SunsetValley.sims3 folder and a SunsetValley.sims3.backup folder. Change the name and delete the .backup extension (e.g. SunsetValley1.sims3), and the backup will be available to load at the Main Menu.

Generally, if the game bugs out as you've described, it's better to quit without saving, or at least to use "save as" to rename the save. That way, you're not overwriting your intact save with corrupt info, and you can revert to it if necessary.

Graphical issues can not be caused by MasterController. Unless your GPU is dying (did you framerate cap it? Tried other games? ) maybe you have bad CC bouncing the graphic engine. Try loading your save with no CC and only NRaas mods installed and see if you get a different result.