Before going at it with the stronger cleaners, try leaving it out in the sun - it may take an afternoon or two or three, but I think you'll luck out and have the stain be gone. Keep us posted on how things turn out. We've had some tough-to-remove stains on our vinyl before (spider poop, blue jean short bleed, etc) and all came out just fine after a few afternoons skiing. Hope your situation ends up as good.
2005 ProStar 197 w/1:1 MCX; Acme #843; 2007 MC ZeroFlex Tower