Need some help identifying this part.

Someone ripped off the black plastic that divides the front window and the tiny window on the rear hatch. I hope I'm describing it right
Anyone know what that part is called?
I'm so baffled as to why someone would take that part off.

thanks for the help

 

B pillar i think..

 

B-pillar exterior garnish. Don't know the part number for the OEM pieces, but the Nismo CF ones are #99993-RNZ30.