You probably saw the 5109. The last four were assigned to Eugene, with 5120 (the newest) being retired in late 1972, leaving the 5100, 5103 and 5109. I have found photos of 5109 at San Jose roundhouse on track 1 dated July of 1973, then another claimed to be at Roseville in August of 1973. A photo dated November 1973 puts it back in Eugene with the stack wrapped in plastic. Another photo from July 1974 shows it at Eugene with the stack uncovered though it was retired in June. Then sold to OP&E as their #14 in September of 1974.

That does explain 5109's trip to California, otherwise it was apparently always an Oregon engine. It has also been suggested that SP had leased one of the P&SR 44 tons to a Bay Area industry, but these were all retired by 1973.

The photo of the 5109 at San Jose has the engine doors open. It does not have its original Cooper-Bessemer engine, so it had either been swapped with a later unit or a new had had been purchased, both common practice.

Thanks for the info as that is a feasible explanation as to its odd sightings in California.