It's probably safer to leave the mark there. Alcohol isn't a good idea - if you decide to try it, be gentle with it and do not bear down on the screen - it is very easy to damage the coating on the panel.

I did a forum search and found answers ranging from using a Q-tip soaked in lighter fluid to a facial tissue dipped in Windex. One person suggested emailing the manufacturer of the magic marker, which sounded like the best idea to me.