how did you wash it? i've been using pencils on fabric for years- it's always come out- when the project is all done; quilted & bound- i wash it, in the washer with warm water & detergent. I also always mark as lightly as possible. if i have a fabric that wants to (hold on to) the pencil lines i spritz them with shout or spray & wash- that has only happened a couple times on fabric that i did not pre-wash- (maybe the sizing or other chemicals in the fabric holds on to it?) anyway- if it's white fabric & other fabrics are not going to run i would try a stain remover--did you (heat-set) the lines by ironing over them? you may be able to put together an (oxyclean) paste & work that into the lines-then rinse well--dawn dish soap works well for removing lots of things---