I believe it is the Rear Body Control Module that can get shorted if cargo lamp isn't carefully replaced. It is suggested to either pull the room fuse or disconnect the wire from the back of the cargo light switch when replacing this lamp. Since the light is working it is probably not a failed fuse. You might even be able to see in there popping open that small door right behind the door latch on the hatch.
I like to do my own fixes as well but if still under warranty you might have the dealer look into it.