Open the program "Activity Monitor", search for your App (just the apps name, not the simulator), click "Informations" and open "Open files and ports". Copy the second entry (something like /Users/me/Library/Application Support/iPhone Simulator/4.2/Applications/B97A9504-0FA5-4826-BB6D-A2335A676459/VSGradientView.app/YourApp). This is the running app, while <...>/B97A9504-0FA5-4826-BB6D-A2335A676459/VSGradientView.app/ is the bundle, and <...>/B97A9504-0FA5-4826-BB6D-A2335A676459/* the sand-boxed folder.
If you pass this as open "/Users/me/Library/Application Support/iPhone Simulator/4.2/Applications/B97A9504-0FA5-4826-BB6D-A2335A676459/" to the terminal, the folder will open in Finder.
Sounds complicated but isn't.