Ouch. I know exactly how that happened. If you can’t get the dough out I think it will just dry up and in 10 years when you have to replace the water heater it can go to the dump as funny looking glue that nobody will be able to identify.
Charles in many parts of the world/country water heaters are placed in laundry rooms, basements, closets, or bathrooms. Frequently the top of a water heater seems like a natural warm spot to raise dough.