THIS WILL HELP!
I just spent the last few hours in total panic after thinking I had lost YEARS worth of Sims data. I downloaded a bunch of mods at once and uploaded them all into my game (NEVER DOING THIS AGAIN). After getting them all in, and excited to see them run, I realized I could load into any of my families, and then I realized that my households were erased in each city. When I tell you I PANICKED. I didn't know what was the issue, or which mod, or anything. I thought it was because I meddled with the Tray folder, that however is less of a concern if you don't actually use your library which I don't.
SKIPPING TO THE SOLUTION
In order to make sure I didn't corrupt any files and totally F up my game, I loaded up my Sims 4, disabled the mods and CC in the game options tab, restarted the game, and loaded into my family with no issue. THIS let me know that my files were there, and all of my families and progress were safe and that it was just one of the hundreds of mods that I downloaded overnight. (There is no way to know exactly which mod it is aside from testing them one by one.) So, I took everything out of the Tray folder (if you have anything that you actually want in your library apparently when it is already placed into the game it doesn't get impacted by the deletion, IF IT IS NOT ALREADY PLACED IN THE GAME AND YOU DELETE THE TRAY IT WILL BE DELETED. I then sorted my mods folder by most recent downloads (sometimes the dates will still be wonky and you will have to look by name hopefully being able to recall what you recently downloaded before your game went to *). I pulled out MOST of the mods I downloaded last night, and then further scrolled and found the ones that were out of place. I TOOK EVERY SINGLE MOD THAT I RECENTLY DOWNLOADED BACK OUT! Went into the gameplay and it loaded up fine. I was able to save my families by going to the 'Load Game' option and loading a previous save from earlier in the night before I downloaded the evil mods. This was my saving grace! Now with all the new mods back out, my old mods are still running fine, and everything is working as it should. I will be deleting the new mods and redownloading them one by one instead so I can figure out which one is the culprit! I will try to remember to come back here and update, but this will solve the main issue at hand for now!