unlike previous versions (3.4) it doesn't actually show what attachments are attached to a post in the media manager when not inserted into post.
Steps to duplicate.
1. create new post
2. add media(audio) and close tab
3. go back into post and it doesnt show any media selected, but if you pull the attachment from the theme its there.
In previous versions of you attached media youd be able to see what was attached to the post
I know theres the created gallery/uploaded to this post, but its not displaying the audio, actually other than going into the media page thered be no way to tell I have a mp3 attached to the post which seems kind of confusing, maybe Im missing something though.