This is the exact kind of situation that made me begin making archival copies of my music ASAP, sometimes before I even listened to it. Someone lifted my book of music cd's from my car the other day, and I just noticed last night.
Lucky for me (how ironic) I made backups of them all, so I can replace them at the cost of burning new ones, however they won't have the great art, and they won't bet the CD's i've spent thousands of dollars collecting.