For the "Lucky Pig of Amelia Earhart," I feel like the half pendant would have been in the Heart Room or the Tomb of Ancient Kings. Considering the guards were in the Room of the Three Gargoyles and the Swamp, the third guard must have been in the Heart Room (the only unentered rooms were the Cave of Sighs- I doubt that both entrances would have had guards- and the Room of Harmonic Convergence- the room with the object). In the event that Kristen went into the Heart Room from the Observatory, she would have been taken out there. That means that Scott would have run into the Swamp guard as the third guard.
The half pendant is not visible in the Observatory, Treasure Room, Shrine of the Silver Monkey, Pirate's Cove, Dungeon, or Tomb of Ancient Kings. Therefore, the most probable places in my mind would either be in the Heart Room, since that room was not entered or shown during the temple overview (but was still active during the run, as evidence of having the third guard), or inside the "Sarcophagus" in the Tomb of Ancient Kings. The only reason I mention the Tomb of Ancient Kings is because it would have been obscured from the camera's view, while still being in an unlikely place that the contestant "should" see. In addition, the other episodes from this layout and this production day were all thought to have the half pendant located somewhere on the ground, so why not put it on the ground in a container that cannot be seen by the television viewer?
Any thoughts?