It's a very corrosive chemical to plastic - it will have melted the top surface of your bath - they used to use Acetone for nail polish removal - I used it on a polyester tie years ago and it just disintegrated.
Where the shine has gone all you can do is polish a new shine onto the surface - lots of hard work rubbing with a cloth and a polishing compound like metal polish or Autosol - the effort required may not be consistent with the reward.
Peccavi, July 2010
