I'm not sure why, but a load of music has suddenly gone missing from my iTunes library. I added a few new albums to different artist folders, and instead of adding each folder to the library individually [using "Add to Library" from the File menu], I decided to take a shortcut and add my entire Music folder to the Library. Now, a load of stuff is missing, and I have a massive collection, so I don't know exactly what's there and exactly what has gone. Searching using Finder confirms that the files are completely gone from my hard drive. Why the hell didn't I use Time Machine!?