- Context Click on the sort column header bar (where it says "Name | Artist | Album" etc) and pick "File: Zip" (assuming it is zipped, otherwise pick "File: Video") (Here is more info on the Sort columns and how to use them)
- on your missing song, look in this column, you'll see the path at which kJams believes the file resides. If it is blank, then, if you showed "File: Zip", then instead show "File: Audio", if that's blank, show "File: Video". Hide them when you're done.
- to discover where the discrepancy is, compare the path in kJams to the actual path to the song as you trace it in the file system. Likely, you've changed a folder name somewhere, or moved a folder.
This should be enough for you to know what happened. If it turns out that the problem was that you changed a path, and you *need* it changed for some reason, you can still recover if you make a symbolic link from the old path to the new path. Otherwise, just change or move the folder back to where kJams expects it. If you renamed the volume, you have to rename it back.
If you've tried everything and it still doesn't work, let me know and i'll fix it.