I've seen strange thing in my system and other one (not mine): both are i386 arch.
$ yum list installed | grep rawhide | wc -l
But they marked as "@rawhide/$releasever", not "rawhide"
I've downloaded full file list from fedora repo mirror and checked some packages. For example:
$ yum list installed | grep rawhide | grep readline
readline.i686 6.0-3.fc12 @rawhide/$releasever
$ cat fullfilelist | grep i386 | grep readline-6.0-3
It isn't testing package, but it isn't in "@fedora" or "@updates" category. I haven't temporary enabled rawhide repo.
the @<Repo id> is set when the package is installed, it have nothing to do is it is available in the "fedora" or any other repo.
You must have installed your F12 from a F12 prerelease, in the yum in F13, you will get @anaconda-InstallationRepo.... for packages installed from installation DVD