Same question was posted a month ago by a different user, but she stopped responding… I have the exact same
Issue.
This is a little complicated. I turned off iCloud Photo Library (for reasons that are unimportant) and the dialog that says "Photos will be removed from your phone, but will remain on iCloud" popped up and I hit "OK".
So 3100 photos were removed from my phone because they were all stored to iCloud.
Then I turned iCloud Photo Library back on, thinking all the 'removed' photos would reappear in my Photos App, but they didn't, and I don't know what to do. I verified that all of the photos are on iCloud by logging into the web interface on my desktop, I just can't get them to show back up in my Photos App on my phone.
Best Answer
Not sure what happened, but they appeared suddenly this morning. They were gone for over a week...and appeared today. Weird...