Pressing way to hard? Really? Well I guaranttee you I press way to hard. I AM Presser Woman! You should see my arms!
but jokes aside. I will not pay money to ruin fabric. I can do that for free.

I am sorry this happened, but I am glad you posted. I think this happens a lot, and people just don't want to post it due to all the "I told you so" responses they may get. It's like playing russian roulette. There's a bullet in there somewhere. I would rather have a 100% chance of less then perfect quilting, than any chance of lines drawn with a magic marker not comming out.
This is not your fault. The only thing you did wrong was to take somones recomendation to use a marker on your quilt. Honestly I wouldn't even use then to draw diagonals that will be a cut line, due to the chemical make up of the ink. It could harm the fabric, as someone noted because it's not acid free.

and before you think I am holy than thou. I once used a quilters pencil to make quilting lines to follow, and that never came out. I decided I need to stop trying shortcuts to prefection, and just let those lines fall where they may - guided by hand to the best of my ability. Well, that, and a chalk pencil! LOL