Raye Penber's fiancée's part opens up a loophole in DeathNote 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?
To L and the investigators, Naomi Misora is only missing


  Light writes down Naomi's name, resulting in her death by suicide. Her body is never found due to the specifications made by Light in the Death Note.


Source: Naomi Misora - Plot (Last Paragraph)

Given that Light specified that she would commit suicide and when L sees Naomi's photo they still don't know that Kira can kill besides a heart attack, there's no way to connect Naomi's disappearance to Kira.

If L was to take a leap of faith and pull out the CCTV footage showing Light with Naomi, what can they do then? Light had a legitimate reason for being at Police Headquarters (in fact it was by pure chance that Light ran into her there, it wasn't planned like with Raye) and if they questioned him, Light could just as easily said he noticed that she seemed depressed and tried to help her which would backup the suicide if they discovered her body.