[ I overlooked this event until now, because the news stories didn't use the word "mirror" anywhere ]

In July 2001, 13-yr old Boy Scout Cody Clawson was lost south of Yellowstone National Park for 18 hours, including overnight.

In a 2015 interview, Cody said that on the following day, he looked for an open space to signal from, then used his belt buckle as a signal mirror to reflect sunlight to the rescue helicopter.[1]

The rescue helicopter was piloted by Star Wars actor Harrison Ford.

Cody's sun-flashing seems to have been overlooked by the news reporters at the time [2-5], though they captured an exchange that may have alluded to it:

"Boy, you sure must have earned a merit badge for this one," Ford said."
"I already earned this badge last summer," Clawson replied.

Requirement 7(b) for the Wilderness Survival Merit Badge is:
"Demonstrate how to use a signal mirror."

[1] (2015) How Harrison Ford Rescued Wyoming Boy Scout 13 Years Ago

http://web.archive.org/web/20150312161118/https://abcnews.go.com/Entertainment/harrison-ford-rescued-wyoming-boy-scout-13-years/story?id=29465745

[2] CBS News, July 11, 2001
https://www.cbsnews.com/news/harrison-ford-to-the-rescue/

[3] ABC News, July 13, 2001
https://abcnews.go.com/Entertainment/story?id=103690&page=1

[4] Good News, August 30, 2001
https://www.goodnewsnetwork.org/harrison-ford-rescue/

[5] Hello! July 11, 2001
https://www.hellomagazine.com/film/20010712225012/harrisonrescue/