Did you try OxiClean in the soak water? I haven’t found too many things that OxiClean doesn’t get out. When I have a stain I apply it directly on the stain and then put liquid detergent on it and swirl it around. That might be a bit too strong for a fragile shawl, so maybe some in the soap water?
I have so oxiclean but didn’t try that. Thanks!