Did that with the most stubborn mark... and I mess with Sharpies all the time... Always like to have a sharpie in my purse or pocket... just in case...
I was so excited when I got a multi color pack for school last year(like 30 different colored sharpies)
BTW- Nail polish remover works just as well... but, you probably knew that... I had to get rid of a doodle on my hand ASAP before my mom saw (she HATES people writing on themselves)