@Zepher_James
I know how you feel about losing your sim this way. I have had a couple instances recently where the active household has completely disappeared on me when reloading after exiting and saving. Both times it has happened, I had a Last Exception (LE) at some point during my play prior to the save and exit. In trouble shooting what happened, I was fortunate as I was able to use a recovered save to get them back so you might want to see if you can recover a save where your sim is still in the game. After recovering the save, I was able to duplicate the event several times. I also use MCCC which shows a wall post when an LE occurs and that let me figure out exactly when the LE occurred and gave me the specific error that caused the LE. Once I knew what and when it happened, I was able to avoid it happening again and was able to go on.
Just in case you don't know how to recover a save, all you have to do is: At the Main Menu, click the Load button and select a save. Just to the left of the Play and Delete buttons there will be another button and when you mouse over it, it will say Recover. Just click on it and it will give you a list of all the versions of that save. Select one and recover it. Start the game with that recovered save and see if your sim is back. If not, do it again with the next one on the list. Rinse and repeat until you find one that has your sim. If none of them have your sim still there after doing that, then try another older save file. Unfortunately, if you go through all your save files and can't find the sim, then that household is lost and you will have to start over by loading the sim from your library if it was a sim you created in CAS. When you create a sim in CAS, the last thing that happens when you exit CAS is that the household is saved to your library so you should have the sim there.
Hope this helps.
