After upgrading to Mavericks, previously installed iLife and iWork apps may be mysteriously missing. I worked personally with a client who heavily uses iPhoto, and after upgrading iPhoto was no longer in the Applications folder.

If the missing iLife or iWork app was originally purchased through the Mac App Store, it should show as a free download after logging into the Mac App Store with the Apple ID linked to the purchase.

If the missing iLife or iWork app was not purchased through the App Store, it will need to be reinstalled from the DVD, or restored from backup. Once the app is back on the Mac, a free update to the latest version should show in the Mac App Store.