How to ensure assigned names in Photos don’t disappear?

One more thing to check - Photos may have opened a different Photos Library, where the faces have not yet been named. You can see which library Photos is using in the Photos > Preferences > General, at the top of the panel.

You wrote: "assigned the names using the get info window on each photo "

Photos has two ways of assigning names: It will depend on the results of the face detection, if the names you assign will remain or may vanish.

1. If Photos has detected a face in the photo and is showing a textfield to assign a name below the face, the names we assign will usually remain assigned.
2. But if Photos has not (yet) detected a face and we add a faces circle manually, this face may vanish, when Photos detects later a face in the same place. Manually added faces may also get lost after a system upgrade that changed the algorithm for face detection.

Which of the two methods have you used to name the faces?

When I am assigning faces, I am also adding the name as a keyword in the Info panel. That makes it easy to check, if named faces have been lost after a system update or when syncing with iCloud. It has the added bonus that I can see the names of the people in the Info and not just a tiny faces thumbnail. See this user tip: How to use Keywords to Back Up the Named Faces in Photos and Improve the Search for People … - Apple Community

Actually the names seem pretty stable-- more so in the last OSs. I think that I might have had some names disappear or get mixed up, but I'm not sure since I am using several Libraries and, like léonie suggested, I can't always keep track of which one is which.

My experience is different, even for the most recent system version. Only the faces detected automatically by Photos seem to be stable, but I have to reassign the faces that I manually circled after each system upgrade. This I horrible for old group photos with people I have met only once in my live, where I can no longer remember who's who .

So have to use the old-fashioned way and have to write into the captions "left to right - cousin A, uncle B ..." etc.

I don't need the named faces for people I can recognize myself. I mostly need them for scans of old family photos, where I have to ask my family members, if they know, who the people are. Or for photos of people I have met when traveling and will never see again.

Before I tag the names for new photos I wait a few days, to give Photos some time to scan the photos for faces. This way I avoid circling faces manually and conflicts, if Photos later detects a face that I already have added manually.

It was file names you re-named, right?

Where were the scanned Photos located when you named them?

What did you find in place of the names you assigned?

Where were they when you noticed the missing file names.

What type of image files are they?

How much free space do you have on your boot drive?

Have you installed and run any "cleaning", "optimizing", "speed-up", anti-virus or VPN apps on your Mac?

How much free space do you have on your boot drive? Sorry I am not a computer literate so I dont know how to check that info

Control (right) - click on your drive's Desktop icon and select Get Info from the contextual menu. In the Info pane you'll see the size of the disk, amount used and amount free:

So it's the People identification that is missing. You assigned names as you imported the scanned photos, right?

Make sure in the View menu the "Show Face Names" is selected.

ingrid hyde wrote: … If putting the names as keywords is the way to ensure they stay that is what I will have to do, but I have to say that naively I thought that an Apple feature would remain stable and consistent but it seems I was wrong.

Actually the names seem pretty stable-- more so in the last OSs. I think that I might have had some names disappear or get mixed up, but I'm not sure since I am using several Libraries and, like léonie suggested, I can't always keep track of which one is which.

The thing is, face names are not a general thing, and there's no real standard in the metadata that every image viewer understands. So if you transfer a picture to another app or to another person, you can't be sure that they get the face names, with the pictures. Keywords are standard, though, and so it pays to add a keyword for the person rather than relying totally on Photos' face names. I periodically open people albums, select all in the album, and make sure the name keyword is on all of them. That's an easy thing to do.

To add another complication, Photos on an iPhone doesn't display keywords, although keywords still work in searches. So because you can't see keywords on iPhones, many of us also put names in captions. Captions also are standard in transfers to other apps.

So, if you only use a Mac, and you don't need to transfer pictures to others, then you may not need that other stuff.