Great to hear that you got the $ covered by insurance. The whole thing made me think that the hotel is trying to get some $ out of guests.
Yes I know that your kid may have drawn on the sheets but then most things can be washed away - there are tons of stain removers available and alcohol - as the other poster said is great for washing ink away (my little girl used a ball point pen draw on our leather sofa) - I cleaned it with some cheapy EDT.
Please update after you received the linen - I'm curious if the hotel gave you back the 'stained' linen.