This is by design. The Card view only displays scenes that start with a Scene Heading. If you change a Scene Heading to a Shot, it's no longer considered a "master scene" but rather a sub-element of a master scene. If you change the Shot paragraph back to a Scene Heading you'll notice that it reappears in the index card panel (or view) -- along with your scene summary, if you wrote one.
NOTE: The Card functionality in Final Draft 10 is far superior to the one in FD7. Information on upgrading is HERE.
NOTE: Live support for Final Draft 7 has been discontinued. You will still be able to install, activate and use FD7 on appropriate computers but email, chat and telephone support is no longer available. Live activation assistance will be available via phone (818-789-6281) and email and chat (links on the left side of this page) until June 14, 2017.