Great news!
I washed my little quilt by hand with an old toothbrush and some Dawn dishsoap in a little bowl, rinsed it and hung it up to dry. NO YELLOW LINES this morning. Yeahhhhhhhhhhh!
Thank you everyone for your help. I will NOT being using any more yellow marker pencils to mark my quilting lines. I will stick with the blue, water erasable pens. Much better for easily removing lines. :-D