Can you recover a build that wasn't saved in the Sims 4?

@Constxllation  No, unfortunately there isn't a way to recover data after a game crash.  In theory, if you had a scratch folder inside Documents > Electronic Arts > The Sims 4 > saves, you might be able to pull the file out of that folder and into the main saves folder, rename it if necessary, and then load it in-game.  I wouldn't suggest playing this forward, but you might at least find you have a build to save.

In practice, however, the scratch folder should be emptied the next time you load Sims 4, and even if the old file were present, there's a good chance it wouldn't be usable.

I know it doesn't help now, but this just underlines how critical it is to save frequently, even when building.  I'd suggest setting a timer to remind yourself, or saving each time you finish a room, or a similar system that gives you enough backups to work with.

If it's any consolation, I've always found that rebuilding something I lost, for whatever reason, is much faster the second time around, if somewhat less fun.