Hi @krist,
That sounds like a nasty Anaconda bug. You could try mounting the encrypted partition from outside Anaconda, then run the installer afterwards. Ananconda should then see the volumes and pickup from there. I do not have experience with LVMs although I hear its pretty cool. In any case, You may find this page helpful for your case.
You should skip the ‘Prerequisites’ Section … I think those tools are already available to the user in Fedora.