My one saved game got deleted

ladykyera999​  Error Code 12 is an out of resources condition, usually but not always due to the game running out of RAM.  It can only use ~3.7 GB before crashing, and saving causes a spike in memory use, so the danger zone where you may not be able to save is more like 3.4 GB.  Sometimes the game appears to save but can't do so properly, which is one cause of saves labeled .bad.

So the question is, how much memory is Sims 3 using as soon as you've loaded one of these saves, and then when you've played it for 15-20 minutes?  You can put the game into windowed mode and check the Task Manager.  If usage for individual apps is showing as a percentage, right-click the Memory header to switch to absolute values.

Error 16 has a few known causes, but these days, it's most commonly related to OneDrive.  So getting rid of it might help there too.

As for the mods, please list the ones you're using.  I don't care about custom content, but it's worth testing without it just to see how RAM use changes.  You don't need to save your progress.