Also this is a problem with Git not GitFlow. In Mercurial, for example, every commit is attached to a branch so it's very easy to follow where the changes happened.
HgFlow already exists and is actively developed: https://bitbucket.org/yujiewu/hgflow/wiki/Home. It even goes above and beyond GitFlow and adds generalized streams and sub-streams. I've never had to use those extra features, but the core model works well.
Mercurial branches are not meant to be used for short-lived feature branches, though. As "hg branch" puts it: "branches are permanent and global, did you want a bookmark?".