Steps to reproduce:

1. Open attached project (sprite_test.zip)
2. Open 'Test' scene
3. Open Sprite Packer window and click 'Pack'
4. Right click on one of 'not packed' sprite assets in the Project view, select 'Find References In Scene'
5. Notice it finds the correct game object that uses the selected sprite asset
6. Now right-click on one of 'packed' sprite assets, select 'Find References In Scene'
7. Notice that no game objects are found, while both of the packed sprite assets are also used in the scene