3751 last traveled to San Diego in September 2008 as part of AAPRCO convention train. That was the second trip involving 3751 to San Diego that year. I saw it in Fullerton on June 1, 2008 on its way south. Bridge work has been ongoing over the last few years. In fact the
Santa Margarita bridge page has an aerial photo of 3751 on the old bridge, likely from June 2008 trip.