Hi Sybil,
I'm so sorry this has happened to your quilt.
If the Dawn dish soap does not work then I would try Grandma's Secret Spot Remover. It can be found at Hancock Fabrics and JoAnns etc. Also do not dry in the dryer until you get the spot out, simply use a washcloth with the soap and then rinse well, and let air dry. You can launder in the washer and spin, but don't put in dryer until checking once it has completely dried. You may not be able to tell if the spot is gone until dry. Once you are sure the spot is gone the you can launder normally but not until then.
Pam M