Barack Obama clutched his handkerchief as he delivered his final address as President in his Chicago hometown: the very place he launched his campaign a decade ago.

But while the world witnessed the outgoing President warn of the dangers of anti-immigrant sentiment, economic inequality and taking democracy for granted, there was a notable absence from the stage.

Michelle Obama and their daughter Malia were there to hear his emotional farewell speech but his youngest daughter Sasha was nowhere to be seen.

This was quickly picked up on and a “Where Is Sasha” hashtag trended on Twitter. People speculated about all sorts of hypothetical things the 15-year-old could be doing, from “setting Home Alone traps for Trump” to physically obstructing the incoming President from entering the White House.

In reality, the reason was as mundane as her school not letting her attend her father’s final speech as US president because she had an exam the following morning.

Michelle Obama as the First Lady Show all 11 1 /11 Michelle Obama as the First Lady Michelle Obama as the First Lady NEW YORK - MARCH 9: Michelle Obama, wife of Presidential candidate Senator Barack Obama (D-IL) addresses the crowd at a fundraising event at the Grand Hyatt March 9, 2007 in New York City. The mass fundraiser of Senator Barack Obama targeted a youthful demographic. (Photo by Michael Nagle/Getty Images) Getty Michelle Obama as the First Lady WASHINGTON - JANUARY 4: U.S. Senator Barack Obama (D-IL) (2nd L) poses for with his wife Michelle (2nd R), Vice President Dick Cheney (R), daughters (C) Malia and Sasha during the reenactment of a swearing -in ceremony on Capitol Hill January 4, 2005 in Washington, DC. The 109th Congress was sworn in January 4. (Photo by Alex Wong/Getty Images) Getty Michelle Obama as the First Lady LOS ANGELES, CA - MARCH 19: Senator Barack Obama and his wife Michelle arrive at the 36th NAACP Image Awards at the Dorothy Chandler Pavilion on March 19, 2005 in Los Angeles, California. (Photo by Frederick M. Brown/Getty Images) Getty Michelle Obama as the First Lady AMES, IA - FEBRUARY 11: Michelle Obama, wife of Senator Barack Obama (D-IL), listens with her daughter Sasha as the Senator addresses a crowd gathered at a campaign rally at Iowa State University February 11, 2007 in Ames, Iowa. Obama is wrapping up a two-day campaign swing through Iowa after announcing February 10, that he would seek the Democratic nomination for President. (Photo by Scott Olson/Getty Images) Getty Michelle Obama as the First Lady DES MOINES, IA - DECEMBER 08: Michelle Obama (L) and talk show host Oprah Winfrey embrace at a rally for Democratic presidential hopeful Barack Obama December 8, 2007 in Des Moines, Iowa. Obama and Winfrey are scheduled to make two stops in Iowa before heading off to campaign events in South Carolina and New Hampshire tomorrow. (Photo by Scott Olson/Getty Images) Getty Michelle Obama as the First Lady CHICAGO - FEBRUARY 05: Michelle Obama, wife of Democratic presidential hopeful Sen. Barack Obama (D-IL), arrives for a Super Tuesday event at the Hyatt Hotel Feburary 5, 2008 in Chicago, Illinois. Polls showed Obama and his rival for the Democratic nomination, Sen. Hillary Clinton (D-NY), in a virtual tie going into Super Tuesday, where primaries and caucuses are held in 24 states. (Photo by Chip Somodevilla/Getty Images) Getty Michelle Obama as the First Lady US President Barack Obama (L) and his wife Michelle (2nd L) meet with Britain's Queen Elizabeth II (2nd R) and Prince Philip, the Duke of Edinburgh (R) during an audience at Buckingham Palace in London, on April 1, 2009. US President Barack Obama visited Queen Elizabeth II at Buckingham Palace on Wednesday while his in London for the G20 summit. Obama and wife Michelle were hosted by the queen for a meeting, the day before the crunch summit on tackling the world economic crisis. AFP PHOTO/John Stillwell/WPA POOL (Photo credit should read JOHN STILLWELL/AFP/Getty Images) Getty Michelle Obama as the First Lady LONDON, ENGLAND - OCTOBER 11: A screen shows the First Lady of the United States Michelle Obama, as girls participate in a live conversation with her and other school girls around the world, via a video link at the Mulberry School for Girls n OCtober 11, 2016 in London, England. A Global Conversation on Girl's Education was a digital conversation with adolescent girls around the world. The event took place in celebration of International Day of the Girl. Girls in Washington, D.C., Jordan, Peru, Tanzania, and the Mulberry School for Girls in the United Kingdom spoke with one another about the challenges they have faced and potentially overcome in attaining an education. (Kirsty Wigglesworth-WPA Pool/Getty Images) Getty Michelle Obama as the First Lady Executive Director of Let's Move! and Senior Policy Advisor for Nutrition Policy at The White House Debra Eschmeyer (L) looks on as First Lady Michelle Obama (C) helps a child harvest sweet potatoes from the White House Kitchen Garden during a harvesting event at the White House in Washington, DC, October 6, 2016. / AFP / JIM WATSON (Photo credit should read JIM WATSON/AFP/Getty Images) Getty Michelle Obama as the First Lady WASHINGTON, DC - MAY 20: U.S. first lady Michelle Obama dances with students from turn around schools during a talent show at the East Room of the White House May 20, 2014 in Washington, DC. President Obamas Committee on the Arts and the Humanities held the first-ever White House Talent Show featuring performances by major artists and showcase the talents of students from schools participating in the Turnaround Arts program which helps to turn around low-performing schools and increase student achievement through arts education. (Photo by Alex Wong/Getty Images) Getty Michelle Obama as the First Lady WASHINGTON, DC - APRIL 06: First Lady Michelle Obama dances with members of the All Stars from from the television show "So You Can Dance" during the annual White House Easter Egg Roll on the South Lawn April 6, 2015 in Washington, DC. President Obama and the first lady hosted thousands of children for the annual White House event dating back to 1876 that features live music, sports courts, cooking stations, storytelling, as well as the Easter egg roll this year. (Photo by Mark Wilson/Getty Images) Getty

Mark Knoller, CBS News White House Correspondent, said a White House official informed him she stayed in Washington.

“Where was Sasha? WH Official says she stayed back in DC tonight because she has an exam at school tomorrow morning,” Knoller said.

The outgoing First Lady put her arm around her 18-year-old daughter Malia as her husband delivered his speech.

“Malia,” Mr Obama said, gesturing to his eldest daughter, "And Sasha, under the strangest of circumstances, you have become two amazing young women.”

”You are smart and you are beautiful but more importantly, you are kind and you are thoughtful - and you are full of passion. And bore the burden of years in the spotlight so easily,” he continued. “Of all that I have done in my life, I am most proud to be your dad.”

Sasha is a student at Sidwell Friends, a private school in Washington which was attended by Chelsea Clinton, Tricia Nixon Cox, and Archibald Roosevelt. Sasha was the youngest child to live in the White House since John F Kennedy entered it as a young boy in 1961.

Barack Obama pays tearful tribute to wife Michelle in farewell address