Why the big secret?

Within the Trump administration, Vice President Mike Pence is known as a port of calm and stability amid the churn of chaos. So on Tuesday, when he abruptly abandoned a planned trip to New Hampshire after he had already boarded Air Force Two at Joint Base Andrews in suburban Maryland, it raised immediate questions.

[...]

Mr. Pence’s aides said that there was no national security emergency or personal health issue that prompted the change. They said that he had boarded the plane but that it never took off. They would not say much else.

[...]

“The @VP never left Washington, DC. There was no ‘emergency callback.’ Something came up that required the VP to stay in DC. We’ll reschedule NH shortly.”

[...]

“It’s not a national security issue,” Mr. Pence’s chief of staff, Marc Short, told reporters at the White House.

It also was not a “personal” or a family issue, he said.

[...]

“When would people know what happened?” reporters asked. “Weeks from now,” Mr. Short said.

  NYT

Why?

Multiple people familiar with what happened offered at least a partial explanation. They said it was related to the place Mr. Pence was scheduled to visit, the Granite Recovery Center, but they did not offer any details.

Will somebody leak the truth?

UPDATE 7/22:  We finally find out.