What happens if you try either of the following...
This basically adds on the answer by Glorfindel:
- Launch the Photos App
- Go to Photos > Preferences
- Select the General tab
- Click on the Show in Finder button that appears below the Library Location path
Does that open the folder in the Finder, thereby revealing it to you?
If the first method doesn't work, try this instead:
- Ensure Photos is not already running
- Press and hold the option key down
- Launch the Photos app, still keeping the option key down
- Let go of the option key when you see the Choose Library window
- This window gives you a number of options, however the last opened Photos Library should be highlighted on the list. If not, select it.
- Now look below the list but above the buttons. You should see a file path listed for where the library is located
Does that file path reveal where your library is located?