I missed that part of the story.
Here’s a bit more detail on how the word leaked out. From the link below:
In a recording of a radio message from D.C. Fire hazmat personnel who responded to the scene Sunday night, a first responder can be heard saying the substance tested positive for “cocaine hydrochloride.” The message was posted by the website OpenMHz, which records and archives radio dispatches by police, fire and EMS agencies.
https://www.cbsnews.com/news/white-house-cocaine-west-wing-secret-service-investigation/