Amy: So we put a little picture of me and a little picture of Sheldon in it.
Penny: In-in the locket?
Sheldon: Yes.
Leonard: That was in a lost and found box?
Sheldon: Exactly.
Penny: Where we hid it?
Sheldon: So really, you gave us three amazing gifts. You gave the locket, the adventure and the realization that Amy and I can do anything as long as we work together.