Raye Penber's fiancée who had come to give the tip about Kira (she deduced most of the Kira's tactics even before L!), and Light Yagami's encounter was missed by the receptionist/L at the police head quarters.
Both were seen discussing about telling her theory to Light's father in front of the two receptionist before she became missing. Most police head quarters have CCTV cameras attached, so it should have been used by the police to get a clue about her before she went missing the day she visited the police. If she was alive after that day, she would have tried to visit the police head quarters again.
As per receptionists/ CCTV cameras she was last seen with Light and Light offering her to give the tip, so he can on behalf of her tell it to his father, even offering his phone. At least the initial investigation should have started with interrogating Light about her. How was this scenario missed by L and his Team? Is this not a goof?