Out of respect for the families, the White House did not allow journalists to cover the event, meaning the first lady was seen in the flesh only by the families and administration officials who attended. She was, according a tweet Trump sent last week, at the White House, "feeling great".
But her highly anticipated return to her role following the break from the public eye will not be open to press, with CNN reporting that the White House event on Monday will not see members of the media in attendance. She is resting comfortably and remains in high spirits.
First lady Melania Trump, from right, President Donald Trump, Vice President Mike Pence and his wife Karen Pence arrive at Andrews Air Force Base in Md.to greet three Americans freed from captivity in North Korea, Thursday, May 10, 2018.
While the simplest reason for Melania's prolonged absence from the spotlight is her recent operation, the internet has been ablaze with more outlandish rationales.
She sent early signals that she will not bow to speculation or public expectations about what she should be doing.
Jim Carrey went back to the drawing board over the weekend, and on Monday posted a new illustration of Melania Trump on his Twitter. The press is not invited, but no doubt we will receive some kind of confirmation from some source whether the first lady was there or not.
Nevertheless, CNN's "Reliable Sources" newsletter on Monday led with a giant graphic of a calendar, placing question marks on each date since Mrs. Trump was "last seen" on May 10. Greene's father was killed in action in Iraq in 2004, which means she is from a Gold Star family and would have been invited to the reception.
Meanwhile, the rumour mill churns online. These range from theories that the first lady had plastic surgery to speculation that she has had enough of political life and fled her marriage.
Several of the invitees commented on the first lady as they left.
The first lady's absence is providing fodder to Trump critics and online conspiracy theorists. "I can't imagine a previous first lady disappearing for 24 days without some level of concern".
Mrs Trump, never one to obsess like her husband about media attention, has laid low before.
Sanders said preparations for a summit between Trump and North Korean leader Kim Jong Un were going well, and the two are tentatively scheduled to meet at 9 a.m. Singapore time (1 a.m. GMT) on June 12.