Robert Bergdahl, the father of Sgt. Bowe Bergdahl, who was captured in Afghanistan in 2009, said during Sunday's event his son hasn't been forgotten, CNN reported.
"[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," Bergdahl said. "We love you, we are proud of you. Stay strong, never give up. We pray for the day that we welcome you home."
Speaking to CNN, Bergdahl said a long beard he sported was a testament to his son, whose official status is listed as "missing/captured."
"The beard is a chronology," Bergdahl said, "of my son's captivity since June 30, 2009."
Four videos have been released since the sergeant's capture by Taliban militants, providing proof of his well-being, military officials said.
The last video, sent in February 2011, didn't indicate where Bergdahl was being held, John Wagner, a U.S. Central Command spokesman, told CNN.
"We are still searching for him," said Wagner. "We are actively looking for leads and information on his whereabouts and his condition."
The 25th annual annual Memorial Day weekend ride draws hundreds of thousands of participants.