What kind of pen? Different inks dissolve in diffent solvents. If it was a sharpie, try a cheap pump bottle of white rain (or equally cheap) hair spray. The carrier to keep the hair spray dissolved just happens to be the same solvent as the sharpies ink. If really persistent ink, pure acetone may work, but you run a bigger risk of bugger in up the inks in the swatches on the quilt with the pure acetone.
Some other inks dissolve better in semi-polar solvents. A really good semi-polar solvent to try is acetic acid, distilled white vinegar.
Last, try a fully non polar solvent, mineral spirits would be the first of these I would try.
Hey, your in the dog house. If one of these works, you might get to sleep back inside again. It's already toast, right? Test small spots that are on the edges of the quilt first to see if they will effect the fabric coloring and the ink. Then go from there.