That sounds great, but turns out my mom (I just bought this computer from her) neglected to set up Time Machine. This is just getting better and getter.

[EDIT] Good news! Although I've changed no files and done absolutely nothing to solve the problem, the uninstaller has magically both reappeared and started to work. I'm just going to uninstall everything & start from scratch. Thanks for your help!

Warning: Long and most likely very confusing.
First things first, I'm using a 2010 Macbook Pro (2.4 GHz, 4 GB) for the Sims 3. I know it's supposed to be awful, but I played the game about a year ago with no issues so I thought it would be just as successful this time. No such luck.
Mistake #1: Installing Sims 3 and 7 expansions, along with 2 GB of cc before even starting the game.
I obviously should have taken this more slowly, but what's done is done. I tried to load up the game, and it never loaded past the blue half-screen with the giant plumbob. The launcher worked fine.
I took out my mods folder and downloads, this time the game loaded up as usual, albiet slowly. I got into Sunset Valley. I quit the game to see if I could put my mods folder back in. Put it in, loaded it up, same thing happened as the first time I tried, only got the plumbob screen.
Mistake #2: I got desperate and saw a tutorial here on how to bypass the launcher. I followed the instructions exactly with the info.plist package. Biiiiig mistake. Tried to load up my game, got some sort of huge error message that the game was unable to load. I didn't get a screenshot of it. I changed the package back to the original state.
Mistake #3: For some reason, now when I click the Sims 3 icon to start the launcher, (explaining this will be rough) you know how a second icon comes up at the very end? Wel, now it just flashes for about 5 seconds, then disappears, loading nothing. http://i.imgur.com/qqRr56C.png Here's what I'm trying to explain. That little thing on the end is a small flashing plumbob, and it makes absolutely no sense.
Also, somewhat related, my uninstallation files are nowhere to be found.
If anyone knows of any solutions to these issues, that would be fantastic, because I'm completely at a loss.

tl;dr I cannot start a game that I also have no way to uninstall.