Okay, I have seen some strange behaviour with displaying bad files, where they just seem to disappear from Smartlists and Views for no obvious reason after a while, but I think that happens when the files are deleted or something.
EDIT: I just tested what happens when I delete the bad files. They do indeed disappear from the Bad File Smartlist and View, because MC has Fixed Broken Links, as per my settings.
Anyway in this case I think I made a mistake.
You see, until a file is imported, MC may not and probably will not know what type the file was supposed to be. So by telling you to restrict the file type listed to "Audio" in your Smartlist, the bad files are excluded from the display.
Remove the "Audio" file requirement from your Smartlist, so that all file types are displayed. See if they now show up.
Note that if any (or any future readers) were using a View to display the bad files instead of a Smartlist, you would need to make sure that it also displays all file types. That means that the View needs to be set to not using the parent View's rules for display if the View was created under one of the existing major headings in the Navigation Pane on the left, for example the "Audio" View group. It is easy to stop a View from using the parent View's rules, just by editing the View and unticking the "Use parent scheme rules for file display" checkbox.
As I don't have any bad audio file to test with at present, I tested this by finding a small video file outside the MC import directory structure, copying it several times and renaming all the copies as mp3 files. I then moved them to the MC Audio import directory. MC tried to import them, failed, and subsequent attempts to import them failed with the "previously determined to be bad". All those bad files appeared in both my Bad Files Smartlist and View. MC didn't know what "Media Type" or "Media Sub Type" they were though, with those tags blank, which is why they didn't display when I had specified the "Media Type" as "Audio".
So try that and let me know if that still doesn't work.