Removing melted plastic from exhaust??

About a week ago while riding, a plastic grocery bag somehow ended up stuck to the bottom of my exhaust system and melted to it. I never saw it and have no idea how long it was there. Likely not too long as I could smell the burning plastic at some point close to home but didn't notice it was coming from my bike until I got into my garage and was able to investigate it. 

Without hesitation I started wiping away the melted residue with my boot, being cautious to not use a part of my boot that would also melt into the exhaust, and I thought I was able to get all or most of it off.

A week later, and several bike washes to try to clean it off, I still smell the melted plastic that's on the base of the exhaust. And it seems that when the bike is cooled off, the plastic is somehow molded into the metal. (this is on the stock system, on the bottom part with the cat - not the muffler or the headers.)

This is so unfortunate and I don't know what else to do to clean or fix this. The smell is awful and it's present every time I ride now.

Has anything like this happened to anyone else? What can I do to completely remove the remaining melted plastic from the bottom of my bike? Not just for the sake of the smell, but that has to be somewhat hazardous as well. 

Thanks! 
DKX