Caliban, that also seems correct, as there was no sign of them in the actual memory management part. In the Mii part the only option to save them was to transfer them to a remote (which did me no good as well).
Heh, in short, even if the SD feature was there I'm not sure I would have been able to save the Miis.
Also, apparently the Wii does try to upgrade itself as soon as you connect it to the internet, but fails. According to Nintendo the servers will not be live until the 19th. This upgrade could solve all of these issues.