Well... the file linuxx86.tar.gz is not where you expect it to stay. You can try to open a terminal and do a search using the find command:
find $HOME -name linuxx86.tar.gz
being logged in as the same user who performed the download.
But neither it nor the 3 rpm packages I've successfully installed are visible from the terminal
I'm not sure what do you mean. If you installed some rpm, you can see if it has been successfully installed, by
rpm -q <package name>
where <package name> is the name of the rpm, without the version number, the architecture and the .rpm extension. If you want to list the files installed by the package:
rpm -ql <package-name>