Version:           2.0.0 (using KDE 4.1.3)
OS:                Linux
Installed from:    Ubuntu Packages

I have two directories added to my Local Collection for Amarok. The one stores my mp3s, the other stores my lossless music (flac).

Sometimes it happens that I get a FLAC version of an MP3 album. In this case, I simply delete the album from my MP3 directory and copy the FLAC version to the lossless directory.

The problem is, that in such cases, as soon as you start Amarok, the album disappears from Amarok's Local Collection and there's no way to find it again.

I noticed that Amarok sees that the files have been changed, since the progress bar pops in for a moment in the bottom left. But after that when I expand the Local Collection tree and look for my album, it's not in there. Also no hits when try to search for it using the search box. I tried "Update collection" from the menu and "Rescan collection" from the settings too. The latter took a long time, but the album's still not there.
I also tried to restart Amarok several times. Still nothing.

The only way to see your album is to delete ~/.kde/share/apps/amarok then start Amarok again. In this case, Amarok rescans the collection again and finally the album appears in the list again.