Missing fashionistas

Exploration Stage: River of Oblivion
From: Detective
Description: No connection was found between the missing people. No ransom was demanded; on the contrary, expensive items were left at the scene, untouched. Oh, by the way, there was a woman's hat in evidence. Have you seen one around here?
Completed: See, this is the latest New York fashion. What woman wouldn't want a hat like this? But the woman who wore it has disappeared. And she left behind a strange symbol on the brand's tag.