Answer

In Simulator

/Users/<YOURUSER>/Library/Application Support/iPhone Simulator/<IOS-VERSION>/Applications/<APPID>/Documents/<your-file-name>

YOURUSER - Username you are logged in as

IOS-VERSION - The one you are running the app under ex. 6.0

APPID - A unique alphanumeric ID given to your app. Once you delete/clean your app it creates a new one.

your-file-name  - The file name that you are looking for.

e.g.

/Users/mvohra/Library/Application Support/iPhone Simulator/6.0/154FCF8C-B259-4A57-B8BB-E9FD3C1851D1/Documents/evaporation-4.jpg

In Device

/var/mobile/Applications/B29607A6-E18B-4CB3-A628-1E81A6C7B1AE/Documents/<your-file.txt>

e.g.

/var/mobile/Applications/154FCF8C-B259-4A57-B8BB-E9FD3C1851D1/Documents/evaporation-4.jpg