A photograph purportedly showing President Trump awarding a Purple Heart to a wounded veteran at Walter Reed National Military Medical Center was widely shared on social media in December 2018, along with the claim that the pictured event went unreported by the "mainstream" news media:
President Donald Trump visits Walter Reed Medical Center, placing a Purple Heart on a wounded warrior injured in battle. This was, as expected, mostly unreported by the mainstream media.
While it's true that the mainstream news media did not publish many articles in December 2018 about President Trump's visit to Walter Reed, but that wasn't because of any perceived anti-Trump bias -- rather, the press didn't cover this event in December 2018 because it had occurred a year earlier and thus was no longer news.
President Trump paid a holiday visit to Walter Reed a few days before Christmas in 2017 and bestowed a Purple Heart medal on a wounded soldier, as the Associated Press contemporaneously reported:
President Donald Trump paid a holiday visit to wounded service members at Walter Reed National Medical Center, hailing them as “some of the bravest people anywhere in the world.”
During his visit, the president awarded the Purple Heart to 1st Lt. Victor Prato of the 127th Airborne Engineer Battalion, who was injured last month while deployed in Afghanistan.
It's not even accurate to say that President Trump's visit to Walter Reed in December 2017 was ignored by the news media. Video reports of the event were published by national news outlets such as PBS News Hour, USA Today, ABC News, HLN and "Inside Edition." The Seattle Times, CNN, The Hill, Fox News, PBS, WRC-TV (D.C.), WJZ-TV (CBS Baltimore), the Boston Globe, and Lohud also published articles about President Trump's visit to Walter Reed Hospital in December 2017:
First Lt. Victor Prato received quite the holiday honor.
President Donald Trump awarded the 25-year-old Somers native with the Purple Heart after he was injured in a car bomb while deployed in Afghanistan in November.
Prato, who played football for Somers High School and Princeton University, received the honor as he recovers from soft tissue injuries at Walter Reed National Medical Center in Bethesda, Maryland, according to the White House. Prato, a member of the Army's 127th Airbone Engineer Battalion, was injured by an improvised explosive device.
President Trump had bestowed a Purple Heart upon a wounded soldier during a previous visit to the Walter Reed National Military Medical Center in April 2017. That event, too, received coverage from national news outlets. Here, for example, is an excerpt from an article on the subject published by the Washington Post:
On a rainy spring Saturday, President Trump paid a visit to Walter Reed National Military Medical Center, awarding a Purple Heart to a soldier who was wounded last month in Afghanistan.
In his first visit as president to the military hospital in Bethesda, Trump pinned the medal on Army Sgt. 1st Class Alvaro Barrientos, who lost part of his right leg. The Purple Heart recognizes service members who are wounded in combat.