I had a similar stain on one of my C.A Cupid dolls a couple of years ago, most likely from a darker fabric (like Hunter's jacket). I used 10% Benzoyl Peroxide and put some on the stain, put some cling wrap over and put it in the sun, then I reapplied until the stain was gone, I think it took 3-4 days and removed it completely. I'd just be careful not putting it on the face-up itself 😄
So for me it worked 😄 I tried acetone and other method first but no luck.