Interior firefighters were making a search separate from other team members to cover more ground. The firefighter fell into the basement and lost his radio during the fall. Command was made aware only because he did not check in at 10 minute PAR. The firefighter could not get out of the basement due to an ankle injury and fatigue. This was the third fire that night. Fresh crews were available but were not called. This house was vacant. No fire in the basement at the time of the event.