Local Package Rooms - Assets Blank

I sent my project to someone else as a YYZ. That person then created a new room, using only assets existing in the project, and then created a local package containing only the new room. When I import the local package / new room back into the original project, it appears in my room list, with the layers and assets seemingly in the correct locations, however all the assets (objects & sprites) are blank / not linked to the assets existing in my project. Also, there's not even an option to...

Local Package Rooms - Assets Blank