I periodically run into this problem. I’ll import a JPEG or PNG photo to the photos app. But, even though the photo shows up in the imported album, it does not appear in the main library. Moreover, if I drag the photos into an album, it shows the + sign indicating that it has been moved into that album. However, the photo never shows up in that album.
Is this a bug? If so, is there an easy fix?
I’ve never noticed this problem. Do you have “Copy items to the Photos Library” checked in Settings?
I’ve found that Photos sorts pictures by date, and when you import pictures, they may be shown somewhere up in the list as the app keeps their original date (from the file itself or from the EXIF data), so they’re not immediately obvious in the library as they will not be sorted at the bottom. Try the Recents smart folder.
This is the answer. The Library view sorts by date and the photo will be inserted into the library according to it’s date (which may be the EXIF date if it exists otherwise the file date).
Yes, but, even when I find the photos via search in the main library, they will not copy over to another album. 
