Ruhl was in a vehicle on Thursday looking for ways to fight the blaze when officials lost contact with him, fire information officer Ken Sandusky said. His body was recovered on Friday.
An autopsy to determine the cause of death will be conducted this week, the US Forest Service said. Ruhl, part of a Black Hills National Forest firefighting team, had been helping California firefighters since June.
The fire had grown to about six square miles by Sunday and was 20% contained.
Three firefighters who were burned on a fire north-east of Sacramento on Saturday have been released from hospital. One has returned to duty and all are expected to make a full recovery, fire officials said. A fourth firefighter remains hospitalised with serious burns.