I agree with the ladies who suggested hairspray. But be sure to use a good, old fashioned hairspray, like White Rain. it works wonders on ink marks.
You will need to keep spraying until the ink begins to fade a lot, blotting every once in a while with a paper towel. the color will appear to run a bit, but that's OK, since it is mixed in with the hairspray. If there is a residual mark, spray it with a stain remover and then wash it again.
I hope the stain didn't set when you washed it the first time!
I've used the hairspray trick on just about every fabric, and years ago my husband tried it on leather car seats when he sold cars and a customer had gotten ink on white leather upholstery. It worked for him, too.