Washington (CNN) -- The parents of missing U.S. serviceman Bowe Bergdahl led the Rolling Thunder ride in Washington on Sunday, trailed by the roar of what was estimated to be hundreds of thousands of motorcycles.
The annual Memorial Day weekend ride, now in its 25th year, is held in remembrance of prisoners of war and those missing in action.
Bergdahl, a 26-year-old army sergeant, was captured in Afghanistan in 2009 after he finished his guard shift at a combat outpost in southeastern Paktika province.
"Bowe, your family has not forgotten you, your hometown has not forgotten you. Your state of Idaho has not forgotten you, and thanks to all of you here today, Washington D.C. has not forgotten you," his father, Robert Bergdahl, told a cheering crowd.
"We love you, we are proud of you. Stay strong, never give up. We pray for the day that we welcome you home," he said.
Flanked by riders wanting to offer support for the safe return of his son, Bergdahl spoke separately to CNN. He sported a long beard and wore a bandana imprinted with "POW." His son's official status is listed as "missing/captured."
"The beard is a chronology," Bergdahl said, "of my son's captivity since June 30, 2009."
Since his capture by Taliban militants, four videos of the Idaho native have been released, living proof of his well-being. But the last video was sent in February 2011, and it's unclear where Bergdahl is being held now, according to John Wagner, a spokesman for U.S. Central Command.
"We are still searching for him," said Wagner. "We are actively looking for leads and information on his whereabouts and his condition."
Bergdahl's parents have spoken infrequently to the public to prevent comprising any negotiations that may be taking place.
People participating in Sunday's rally expressed support and encouragement for the Bergdahl family.
Retired army Sgt. Kevin Coffey rode in on his Ultra Classic copper pearl Harley Davidson from North Carolina with the Rolling Thunder Chapter 7, the group that sponsored the Bergdahl's participation this year.
"I would hope that he would know that he is not forgotten, that somebody is looking for him now," said Coffey.
Wayne Daniels, retired from the Army, outfitted his handcrafted Model T car in honor of soldiers lost in action and missing. He choked up when describing the moment his NC7 Rolling Thunder chapter asked him to drive Bergdahl's parents in the lead vehicle. His three children and girlfriend didn't hesitate to give up their usual seats and stand on the sidelines and watch this year.
"I want to make (people) aware of who we still have missing," said Daniels.
Adam Levy contributed to this report.