How to recover Mountain Lion's dmg file after installation? I downloaded Mountain Lion from App Store and installed it.

I have not set Time Machine and I installed Mountain Lion one hour ago (since posting this question).

The dmg file is not in Applications folder anymore.

How to recover Mountain Lion's dmg file after installation?
After Mountain Lion is installed, your Mac auto-deletes "Installer Mountain Lion.app". So before installs or upgrades like that, you must make a backup (compress it and move file compressed to anywhere, where you put storage data).

And now, you need to download "Installer Mountain Lion.app" again from the App Store.