I get the following error in Photos app on my Mac.
Missing File Photos with unavailable original files cannot be opened. The original photo “IMG_3076.JPG” is either offline or cannot be found. Click “Find Original” to reconnect.
This is what has happened, I assumed that since the photo is in the Photos Library I could delete the file from the hard drive. Apparently not. The answer by @Tetsujin suggests that this is not the case.
I have a backup of all these files and I can restore these.
My question is, How do I import these files into the Photo Library completely, so that there is no longer any need to keep the file as well?