Some photos from iCloud Photos after backup mysteriously disappeared
Yes - sign in to iCloud from a computer browser and you can see all photos that have been deleted in the past 30 days (or a little more some times).

iOS and macOS version of Photos can also show the deleted items album if you toggle it in preferences or choose it if it’s enabled.

This is covered in the “What if some photos are missing” section of this guide to iCloud Photos:


https://support.apple.com/en-us/HT204570


Barring that, you’d need a backup from before the photos were deleted to get them back.