win64
Broken: 2.72.3 83cbcef (latest win64 buildbot)
1. Open the attached blend. {F130788}
2. Delete the active scene.
3. Note that the Cube's mirror modifier functions correctly, despite the mirror object not being linked to a scene.
4. Save the .blend
5. Reload the .blend; The mirror object has been garbage collected, resulting in data loss.