Beyoncé's World Humanitarian Day performance (Cliff Watts)

"Who doesn't love World Humanitarian Day?" actress Julia Stiles asked rhetorically as we rubbed shoulders with VIPs in a roped-off, sequestered area of the United Nations. (Though it's not as if there is some area of the UN that is not sequestered or roped-off.) We were mingling in the small atrium before being filed in to the General Assembly, where we were to watch none other than Beyoncé perform and shoot a video for her song, "I Was Here," the official song for WHDay, August 19th.

Ms. Stiles told us that she and her friend had plans to celebrate the important day in their own way.

"We want to start a worldwide hootenanny!" Ms. Stiles exclaimed, giggling.

Her friend laughed, nodding her head to indicate that this was a for-real thing that the two of them had actually discussed.

"A worldwide hootenanny," we mused. "Now, would that involve jug bands?"

"I guess that depends on what part of the world you're living in," Ms. Stiles replied.

For those who don't know, World Humanitarian Day, celebrated on every August 19th, was created to recognize and honor those working in humanitarian efforts, and those who have lost their lives doing so—specifically the 22 people who died in the bombing of the Baghdad UN headquarters in 2003.

"Are you excited to see Beyoncé?" a young woman asked us. "She's so nice. One time she showed up—completely random!—with a bunch of carolers at my dad's Christmas party."

We hoped we weren't imposing, we said, but would this lady mind telling us who her father was? He who was able to get Beyoncé to perform at a holiday gala?

"Oh, his name is Edgar Bronfman," Hannah Bronfman replied. "He was kind of a big deal in the music business for a while, but now he's kind of a recluse. That Beyoncé thing was definitely not the norm in our house."

Neither was this a normal Friday night at the United Nations, as Anderson Cooper noted when he took the stage to bring on the evening's guests. "Unfortunately, you won't be seeing me dance to 'All the Single Ladies,'" Mr. Cooper quipped. "You''ll have to come back next Friday for that."

That night, the crowd was introduced to several humanitarian workers for brief Q&A, from the UN's Valerie Amos to Erin Dinan, founder of "One Sandwich at a Time."

But the real shining star of the evening was, of course, Beyoncé, who appeared on stage wearing a twinkling white dress, the walls surrounding her turning into an IMAX explosion as she sang "I Was Here." Suddenly we were transported to Africa, then Asia, then many other locations in the world as giant pins popped up on screen, reminding us that someone, indeed, had been here.

David Droga, whose ad agency Droga5 worked with the United Nations to put on the evening's show, as well as the upcoming Humanitarian Day's "I Was Here" campaign, which will feature the infamous Thunderclap technology to sync supporters' tweets come August 19th, said that he was impressed by the Beyoncé booking.

"They told us to shoot for the moon," the director told us after the event.

They may have missed that celestial body, but they landed an even bigger star instead.