Did you search the old Library package (via Finder) for any of the files by name (assuming you either didn't rename them or know the names under which they were imported)?
What exactly disappeared? The record of the Image in the Aperture database, or the files the record pointed to? What else do you know?
They disappeared from library pane & database (just checked). They didn't show up in 'Recent Images' or 'Last 12 Months' default folders. All images are managed, not referenced & reside(d) on SATA drive. All of September's images & the first month of October are those in question. They were there one night & gone the next. My last vault backup prior to incident had all of the images. I'm stumped. I was getting "inconsisitencies in library' prompt prior to. I did rebulid database as well.