Boo, I did the exact damn thing with a Startron additive I put in the tank for the winter. From three feet away, the wind blew the little plastic/cardboard sealcover from inside the cap right into my full gas tank....really pissed me off. I am bringing it down to the dealer to have it removed along with the tune-up I usually get before I go back riding again in the spring. What a nuisance....
Sorry to hear that. I know first hand how troubling it can be. If you decide to tackle it yourself, I will tell you how I got that cardboard seal out of my tank.
I went to Harbor Freight and bought digital display tool. With a 20% off coupon, I think it was about $50-$55. It has a glass lens and the gasoline did not appear to damage it. I siphoned as much gas as I could from the tank. I inserted the display tool and spotted the small disc lying on the bottom of the tank. It was small and flat so I had trouble getting hold of it. I decided to use a long piece of wire sharpened to a pin point to see if I could "stick it". I did and it worked. I slowly and carefully remove the seal. I had to remove the under seat pan and take the screws out of the top of the fuel pump to lift it up enough so I could get a straighter shot at the disk. I was relieved when I got it out.