The couple said they firmly believed their son would not have voluntarily disappeared.
“It’s out of character for him,” Ken said.
“He’s a soldier, it’s in his nature to go out with mates, go everywhere, city breaks on his own, but he always comes home.”
Kerstin Rudd said he had no reason to disappear and “he was enjoying it in the Army”.
“We think something happened that night and we don’t know if it was an accident or if it was something more sinister, because there’s nothing to show what happened.”
North Yorkshire Police have previously said officers remained “open minded” about his disappearance but added “we must accept the possibility that Ryan has entered the River Ouse”.
In a statement, the Army said: “We can confirm that Lance Corporal Ryan Rudd was reported missing to North Yorkshire Police on 1 March 2026.
“An investigation is under way and we are working with North Yorkshire Police who are leading this. We are unable to offer further detail at this time.”