May have been the one that "helpfully" deleted your music, and replaced it by compressed version, even if you didn't bought it via iTunes. Or deleted your files

May have been the one that "helpfully" deleted your music, and replaced it by compressed version, even if you didn't bought it via iTunes. Or deleted your files period, if it detected a not so "equivalent" version you could download. Supposedly to save local disk space. I recall an accounting of a composer losing his work file that way —they got compressed behind his back. Thank goodness he had a backup.