I've said it many times, but it bears repeating: We should all assume that there are 'no radio' aircraft out there, because they literally aren't fitted with a radio or, if it is fitted with a radio, it's malfunctioning, is tuned to the wrong frequency or is otherwise the subject of finger trouble in the cockpit
Been guilty of that
LB, returning to fixed wing flying was getting checked out in a Cub using the dirt cross runway at Latrobe, instructor hopped out and sent me solo, preparing for take off a SAAB landed on the bitumen, never heard him.