A vigilant Reddit user has noted that Lego The Hobbit (2014) and Lego Lord of the Rings (2012) have been removed from Steam and other digital stores. This means they are no longer available for purchase, but if you own the games you still have access to them. Given both these titles feature content taken directly from the movies, it is likely that the license for this has lapsed as Warner Bros still holds a license for the work of J.R.R. Tolkien, given the more recent Shadow of Mordor and Shadow of War titles.
With no official word about why they've been removed we can only speculate, but still, it is sad to see games removed in this fashion as it is a reminder of the nature of the fleeting nature of the digital landscape.
Thanks, Gamespot.