KDFC is the non-commercial classical music station of the University of Southern California (USC) in Los Angeles. Actually it's a simulcast of 4 stations in San Francisco, the North Bay, the South Bay and the Monterey Peninsula. USC also has its own local classical station(s) down there, with its own separate programming (except overnights, where they all run a common "California Classical Overnights" program).
As David wrote, the most probable reason is someone with a PPM came up north for a few days and tuned in one of the KDFC's, or one of their Southland presets landed on one of the KDFCs and they just stuck with it for awhile.