@Elwood
Didn't happen to me.
Anyway, if you don't have a backup to fetch a recent prefs file and Sitelist from, it should still be easy to recreate your servers manually.
The Hyperion one for public OS4 updates is update.amigaos.net, and the public third-party one is
www.amiupdate.net.
The credentials for the Hyperion updates are the same as your login credentials to your account on hyperion-entertainment.net; if your Sitelist is not intact, you should be prompted for them the first time you try getting any updates from there.
(I don't remember if you're still an OS4 beta tester, but if so, you know where to ask for info about that.)
Best regards,
Niels