JIM Rockford, private detective in NBC-TV’s popular The Rockford Files, is in trouble. He is driving along in rural northern California on routine detective business, when his ear suddenly hits a big bump and is incapacitated. Rockford, who is used to life in Los Angeles, is frantic. There he is, in the middle of nowhere, without any means of getting out: no taxicabs, no rental ears, no buses, no limousine service, nothing.