Somebody waited 2 days for the fire to quit smoldering and then went there and just picked it up and walked of with it.
Of course the simplest solution won't work for a modern Star Wars movie, so it'll involve some Agnes Nixon bullshit about long lost Uncle Vader who was presumed dead but had secretly run off and married Leah's mother's evil twin so they could raise Luke's son as their own after substituting Hahn's nephew for the real one.