Open Finder> Goto following path
Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs
Here, you can see all your simulator SDK's.
Now, here is the trick which I follow.
- Goto the above path of your older version Xcode(say, Xcode 5.0.2) where you've all the downloaded simulator SDKs.
- Copy the SDK folder(s) of required simulator.
- Now, goto the above path of upgraded version Xcode(say, Xcode 5.1) & Paste the SDKs.
- Relaunch simulator.
Hardware>Device>iPad/iPhone should be showing what you are looking for. Also, relaunch Xcode to update simulator list.