The second go-round in the wash seems to have done the trick. The Ralph Lauren top is still wet but the stain appears to be gone. Thanks to Lisa who admonished me NOT to rub because I was ready to scrub away if this last trip through the wash didn't work.
I guess I was a bit obsessive about the top because I had some cool vintage clothes when I was around M's age that were given to me by my Nana and I treated them like rags. I didn't realize what I had until years later. A 15-year-old doesn't have the proper appreciation for a silk Pierre Cardin suit.