Music files lost

My ClipZip froze up on me the other day so I did the 20-second re-boot. Once I fired it back up I discovered all my music folders were empty, I had about 4GB out of an available 8 on it. I hooked it up to my computer and according to the little “fuel gauge” I had a device that was 1/2 full to capacity, browse the music folders, nothing. Anyone else have this happen?