I've not seen this little mishap before so we'll have to work through options to recover.
If you have an external drive you can install OS X using the Recovery Drive on the external drive. While booted from the external drive you should be able to see your internal drive files.
It might be possible to move it back from Applications (Launch Pad is a view of your Applications folder), but I suspect this will fail. You will be able to recover your files to the new OS X on external drive. Once your data is safely copied over, wipe the internal drive and clone the new install to the internal drive.