Pure speculation but I would try something like Murphy's Oil Soap or Dawn Dish Soap to try to loosen up the sealant so it can be removed. If that didn't work I'd try a mild solvent like vinegar (diluted) or perhaps Hydrogen Peroxide (applied carefully). Maybe even some alcohol if all else failed.
If you are able to remove the sealant, here's the stuff you want:
Permatex Flowable Silicone Windshield & Glass Sealer
I hope it works out for you.