Light Mapping Question - Individual objects/prefabs

I have many small room prefabs that each contain point lights. I want to lightmap each individual room. Every time I save it as a prefab and delete it from the scene and try to re-instantiate the room, the light mapping either disappears or is extremely jumbled depending on the location I instantiate it at. To be clear, I simply want to lightmap everything inside the individual room and do not care about the exterior. Any suggestions?

Thanks in advance.

EDIT: To clarify further, is there a way I can lightmap a prefab in once scene and instantiate it in another with the lightmap still on it?