Aperture organises the "Masters" folder by the date of the import session, not by the capture date of the photo. So probably all your earlier original image files will also be in the "2009" folder, since you first imported them in 2009.
The Import session of an image is one of the Metadata fields in the "Aperture" section of the Metadata tags. You can edit your Metadata presets to show it in addition to other Metadata tags.
In the example above the image was taken in February, but the master folder will show it in the folder
I guess missing only 100 photos out of 30,000 isn't a bad record, right?
That is good, but finding the pictures would be better.
In what way are the image files missing? Don't you see them at all in your library? Or do you see black thumbnails with warnings about missing original image files?
Sometimes images miraculously reappear when you rebuild the library - if there are orphaned originals in the Aperture library, they will be collected in a project named "Recovered ....". So you could try, if rebuilding can retrieve some files, but make sure you have a backup of your library before rebuilding.
I started off using iPhoto. In 2009, I started using Aperture.
Do you still have the original iPhoto Libraries, to check, if you really imported everything?
They are photos from 2002, and I remember a while back having trouble with them displaying properly. They were acting like corrupted files. Sometimes they would display correctly, sometimes as static, sometimes as other photos. It was very odd. Now, they display as offline empty frames. I remember spotting them in some folder at some in the past year and thinking, "I should mark this location" and of course, didn't mark it. I'm going to check my old PC today and see if they might be there. I went all thru the Masters looking at the import session from Metadeta and could not find it anywhere.
I don't have the old iphoto Library either. That is long gone.
Now, they display as offline empty frames. I remember spotting them in some folder at some in the past year and thinking, "I should mark this location" and of course, didn't mark it.
- If they have been imported into Aperture as managed, but Aperture lost the connection, rebuilding the library may recover them, if you are lucky - launch Aperture with the ⌘⌥-key held down after backing up he library.
- If they have been imported as referenced and the connection is broken, you need to locate them yourself.
They were acting like corrupted files. Sometimes they would display correctly, sometimes as static, sometimes as other photos.
If they really are corrupted, your best bet would be to find the originals on your PC, like you are planning to do.