See this document: Accept iLife: OS X: About OS X Recovery http://support.apple.com/kb/HT4718
Scroll down to : "Restoring iLife applications after Internet Restore of OS X"
Try to download again from the Purchased tab at the App Store.
Restoring iLife applications after Internet Restore of OS X
If your computer came with OS X Lion or later and you erase your hard disk and install OS X, you can download iPhoto, iMovie, and GarageBand from the Mac App Store.
- After installation, start (up) from OS X.
- Choose App Store from the Apple menu.
- Enter your Apple ID and password when prompted.
- Click Purchases.
- If you haven't previously accepted your bundled iLife applications within the Mac App Store, you should see your iLife applications appear in the Accept portion of the screen. Click Accept.
- You may be asked for your Apple ID and password once again. Your iLife applications now move to the Purchased section. These applications are part of the software that came with your computer. Your account