@SongOfTheSky I hope you were able to recover your lots/builds. Did you upload them into your personal library/gallery? If so, you can place them on to lots in your game from there. If not, It may be a bit of the lesson I've learned the hard way too many times... backup anything you really don't want to lose. Uploading the lots and households you created into your gallery library is a nice backup for the scenario that you're facing now (Though that is also saved to your game tray file, I believe, so is also losable in some situations. One time I deleted mine while trying to clean out cache, etc. Oy, vey!). I would also highly recommend that you keep 2-3 of your last game saves (maybe the file at the end of a day of playing much or adding content you don't want to take a chance of losing).
If you have a backup you can roll back to a date/version without the issue if you have a bug/glitch issue come up, or something's missing, etc. and not completely lose your game...
How to backup your game file:
Go to Documents > Electronic Arts > The Sims 4. Right click on the file "The Sims 4", copy it. This file is your backup of your game saves, etc. You should save a copy of this folder occasionally in case your game or computer crashes. Save it to an external drive (in case your computer crashes - yes, I've had that happen an number of times also). On an external drive it is safe from that.). That way you could add this folder into a fresh install and recover your lost game should you need to.
When/if you need to overwrite the folder (missing content, grave error, bugs, etc.), just go back to Documents > Electronic Arts and drag/paste the "The Sims 4" folder you saved into the "Electronic Arts" folder and tell it to replace (not merge) the current "The Sims 4" folder.
Anyway, I hope you found the lots/game save, and have fun with your new expansion pack!
