See here for further info: About OS X Recovery. Step 2: Find the installer in your Applications folder and right-click on it then.
MAC OS MOUNTAIN LION DMG INSTALL
Regarding "Where is the disk image hidden?", the Recovery Partition is a minimal bootstrap that connects to a wi-fi network to download the complete OS X 10.8 install, that's why it is so small. Download OS X Mountain Lion from the Mac App Store, but dont install it yet. From there, you are offered all the same utilities and functions described above. Next, OS X Internet Recovery will download and start from a Recovery System image. OS X Internet Recovery presents a limited interface at first, with only the ability to select your preferred Wi-Fi network and, if needed, enter the WPA passphrase. The system runs a quick test of your memory and hard drive to ensure there are no hardware issues. OS X Internet Recovery lets you start your Mac directly from Apple's Servers. If you happen to encounter a situation in which you cannot start from the Recovery System, such as your hard drive stopped responding or you installed a new hard drive without OS X installed, new Mac models introduced after public availability of OS X Lion or OS X Mountain Lion, automatically use the OS X Internet Recovery feature if the Recovery System (Command-R method above) doesn't work. See OS X Internet Recovery for more info about the procedure, quote: You replace the HDD and start with Command-R. Use Mountain Lion's Internet Recovery procedure, all files is downloaded and installed on the new drive without having any files. You don't need to worry about having to copy any data, making USB sticks or having the media present.