[2D] [Animation] Prefab referencing PSB is missing from scene when imported from another project

Steps to Repro:
1. import a PSB for rigging/animating
2. use the Skinning Editor to properly rig the PSB (e.g. create bones, geometry, and weights)
3. add the rigged character PSB prefab to a scene and save the scene
4. export the scene and character files as a package
5. open a new project and import the package
6. open the scene and look at the prefab

The PSB character prefab is missing from the scene.