try rubbing alcohol?
from wikipedia:
Removal from surfaces
Though Sharpie ink will become permanent after setting, it can be easily erased for several hours after writing on many glossy (non-porous) surfaces, most readily smooth metal and glass. On mirror glass, simply soaking a cloth in water and rubbing it hard on the Sharpie ink will remove the ink. Since the ink is based on propanol, butanol and diacetone alcohols; denatured alcohol will remove permanent ink writing from almost all non-porous surfaces. WD-40 will work moderately well on recent markings if alcohol is not available. Sharpie ink that has dried for more than several hours can be removed with acetone, but due to the power of the solvent, acetone may damage the surface material. On some surfaces, the ink can be removed by coloring over the ink with a dry erase marker and then removing the Sharpie ink and dry erase marker ink with a dry cloth. Steam cleaning has proved effective also, as well as rubber erasers. Magic Eraser has also proven somewhat effective on hard surfaces such as brick and very effective on wood furniture[5].