CAMERON: I'm interested in the ancient muzzle-loading rifles used during the Modoc Indian War.
LIBRARIAN: Uh, in the California room.
It seems this exchange was just an excuse to move the characters into a room with old Los Angeles photographs. Which the creators could've done in a million different ways. But still, they chose this way.
People have claimed that Summer Glau is part Native. Did the writers include the Modoc line as a sly wink to Summer Glau's fraction of Native blood? Did she come up with this line, perhaps ad-lib it, because of her Native awareness? I don't know, but it would be nice to think so.