How did you "Find many originals in a Photo Library ", if Photos does not show them? Did you look into the library package with "show package contents"?
You may want to check, which library has been opened by Photos. You can see the path to the currently open Photos Library in the Photos > Preferences > General. At the top of the Preferences panel is the library location shown. Sometimes Photos may be showing a different, older library than we think we opened.
Another possibility: If there are originals in the Photos Library, that Photos cannot show, the library may have become damaged, for example by being stored on an incorrectly formatted external volume, or damaged by a third party application, that has accessed and modified the library, for example programs to remove duplicates may do that.