In chapter 9 of the hobbit, why does Bilbo say "I am like a burglur that can't get away, but must go on miserably burgling the same house day after day?"

When the dwarves are imprisoned by the Elvenking, Bilbo is trapped unseen and must rely on the ring to keep him hidden. He wanders the corridors and follows the kings men when they go out to hunt, but he is completely isolated because he can't allow himself to be seen. The wandering and hiding felt like he was burgling the same place everyday, although he had nothing to show for it.