Comment 6 for bug 430672

So it isn't entirely 'we lost it', the rename of the directory on disk succeeded but the rename in the dirstate failed.
If you 'mv a/a a/d' then it will show back up.
$ mv a/a/ a/d
$ bzr st
added:
  a/d/

If we didn't have implicit removals for 'missing' entries then 'bzr commit' would probably block on this.

Anyway, I agree it is a serious thing which should be fixed. It certainly is present in both bzr.dev and the 2.0 series.