We'll leave aside for the moment why in the world I bought a white sweatshirt and move along to the stain remedy.
Long ago, I acquired a chart which listed such items as ammonia, baking soda, lemon juice and glycerine in an arsenal of stain busters. Glycerine is key here, being one of the only substances I've found that can remove ball point ink from fabric. I worked with glycerine, and a mixture of glycerine, dish detergent and ammonia, off and on for an hour: applying, rubbing, rinsing, reapplying. But in time, and with effort, the ink stains went away.
I'm wearing the white sweatshirt again. Is it my imagination or does it look even creamier and more pristine than it did before I defaced it? I think it does.
(Imagine the stain potential here.)