Z: "I think I have Martha's old lunch box."
Me: "What do you mean? Who's Martha?"
Z: "A girl at school who had the exact same lunch box as me last year."
Me: "Oh, so she had one like yours? Cool."
Z: "No, I mean I have her exact same lunch box. We bought it at the thrift store, right?"
Z: "She gave hers to the thrift store. I have Martha's old lunch box."
Me: "Oh. Well. That's cool."