Find (possibly) missing RAW files?

You could try the following to see if the RAW files are in the library package but are not recognized by Photos:

Starting Over From Scratch With a New Photos Library.

1 - launch Photos with the Option key held down and create a new library.

2 - open your old library package with the Finder as shown in this screenshot:

3 - locate the Master folder in the old library and drag it onto the Photos icon in the Dock.

This will create a new library with the same Moments as the original library but will not include the metadata, albums, books slideshows and other projects.

Note: your current library will be left untouched for further attempts at a fix if so desired.

Once the import is complete verify that the new library has all of your photos and working properly before deleting the older, problem library.

If the RAW files are there you can export the RAW files to a folder on the Desktop and import them into your current, working library.

There is no way to check what was or was not there except to restore a backup and look at it - and likewise if you are missing photos then you need to restore a backup form before they were deleted

with Photos that are shot in RAW plus JPEG in Photos they are stacked and will either display a J or R badge to show what the original for editing is - you change this by opening the photo to edit and then under the image menu select either use RAW for original or use JPEG for original -

And if your improperly disconnect of the EHD corrupted the library you may be able repair the library (backup up the library and then hold down the option NS command keys while launching Photos and repair the library)- if you are using iCloud Photo Library this will trigger a totally upload =of the library to verify its integerity

LN

The RAW and JPEG are uploaded in different sessions (separate SD cards), so they show up side by side, only in this case there's no RAW.

Do the JPEGs you are seeing show a J badge? Photos may have stacked the pair after repairing the library, even if you imported the RAW and the JPEG separately. Check this by opening one of the JPEG images in Edit mode. If the pair has been stacked, you will see the command "Use RAW as Original" when you are in EDIT mode.

When I tested Disk Drill (http://www.cleverfiles.com/), it worked well to retrieve missing image files.

Most recover software has a trial version. You can check, if photos will be recovered in the Trial version, but if you want to save them, you have to purchase the app.

If you want to use recovery software, stop using the Mac immediately. Any application, that is writing to the disk, may overwrite data, that could be recovered. Recovery software is not of much use, if the files have been accidentally deleted a long time ago.

Is it possible to make the new library only with a certain group/period of photos?

Yes. Just select the subfolders in the Masters folder for the time frame you want in the new library and import only them.

Do the JPEGs you are seeing show a J badge? Photos may have stacked the pair after repairing the library, even if you imported the RAW and the JPEG separately. Check this by opening one of the JPEG images in Edit mode. If the pair has been stacked, you will see the command "Use RAW as Original" when you are in EDIT mode.

I have an image with the J badge, but no associated RAW file. This is really weird and I can't get the J to disappear.