As a user it is difficult to understand what "Types" that are supported. Maybe it would be a help if there was a dropdown like in Project Browser with all the supported Types?

To reproduce:
- Open attached project and launch "Example - Lighting"
- Set the Hierarchy to "TransformSort"
- Drag an object (e.g. Canvas) from Hierarchy to "Assets" folder in Project Browser
- Observe that a prefab is created
- Drag the prefab from Assets folder to Scene View
- Right-click in the Hierarchy search field and select "Type" as search criteria
- Type "Prefab" in search field and observe that nothing is listed in the Hierarchy Window
- Observe also that the prefab is actually shown in Scene View

As a user the following questions pops up:
- What types are actually supported?
- Are the Types the same as in Project Browser?

Additional comment: The documentaion did not reveal much information either on this issue: http://docs.unity3d.com/Documentation/Manual/Searching.html