So, we learn through the course of the movie that
The briefcase The Dude was given was a fake, The Dude kept The Big Lebowski's case in his car, his car got stolen by Larry, Larry abandons the car, and a vagrant sleeps in the car.
All well and good, but:
There's no indication of what happened to the briefcase at the end of the film. It went missing at some point but neither Larry nor the vagrant would have had any real inclination to steal a locked briefcase, let alone one filled with phone books.
So my question is: is there any indication of where the case actually ended up? It seems odd that a Coen Bros. film would just stop caring about a locked briefcase, regardless of its contents.