I'm an active member of the forums and I do not remember ever "giving ownership" to any other user.
That said, all users are free to do what they like with my map (and all other content made for BL) as they see fit. I would, however, appreciate being given credit for the map, especially if the current "author" continues to use the media I created for the map. I'm pretty sure I put my name (and Laramere's) on the loading screen of the map; has this been altered or deleted?