I'm trying to make a world in CAW and I've been playtesting and building lots as I'm working on the terrain sculping. I decided that I wanted to see how it looks like in game, so I exported it and it automatically updated the world to the new version, I think? instead of just creating a new world separate from the old one which is what i expected to happen. (i do not remember exactly what i did, but the downloads folder did not have a new sims3pack file there, only the old one.) if i try to import a new world now it doesn't work, the file doesn't get replaced automatically and it says the package is already installed when i try to put it into the downloads folder. no idea what's going on with this.

I would hate to lose all of the progress I've done on the lots that I didn't get around to saving, is there a way to go back? The save file is now greyed out and says content not available (obviously, as the world it was in doesn't exist in the game anymore). I think that I have a backup that should be identical to the world I was building in, is there a possibility of using that? Or somehow exporting the lots from the save game?

Can you find the backup of save in CAW folder? It should be at the same folder of your saved world and the name of folder is end with date and time.
Try to export the older version of your world. Then uninstalling the latest version from launcher and installing the older version.
Please be reminded that you need to backup your save folder (Sims 3, not CAW) before you uninstall the world. If the launcher warn you that the save file will be removed. Just click yes and then recover the save from backup.
Hope this help.

There is also a file CAW's installation folder called "worldbuilder", where you can increase the number of backups that the application generates for specific world.