evolution: unmatched folder defect

I have the latest evolution mail reader installed on xfce4 on OS 13.2. I have 2 problems with the Unmatched folder:

  1. there’s a message which is persistently not found in the folder, and hasn’t been found for a week.
    I’ve searched all the messages (using grep) and the mentioned message ID doesn’t appear anywhere.

  2. There are a lot of messages listed in Unmatched without details, but which have all details when opened.

Is there some way to rebuild the Unmatched folder (it can’t be deleted) to clear these defects?
Is there a permanent solution?

screenprint of both defects: https://dl.dropboxusercontent.com/u/45652577/evolution_unmatched_20150403_16%3A24%3A47.png

David