After his horrible meal, he went to another house, which was in fact a farm house. He checked the electricity was still on, and then knocked at the door.
He went through his spiel again to the farmer's wife who had answered the door, but said "I no longer have anything to demonstrate with, but with this being a farm, perhaps you have some wheat or something?" The farmer's wife found a sack of wheat, and he took a handful of it and threw it on the ground. However, try as he might, the high-powered vacuum cleaner simply would not clean it up! He got a little frustrated, then looked at the wheat and noticed it was a little damp. He thought for a moment, and as he was thinking he noticed another sack that had been sitting by the radiator in the hallway. He asked the farmer's wife if he could try with that wheat instead.
She rolled her eyes, and said "OK... but this is your last chance". He took some of the wheat from the new sack, and poured it onto the floor, and the vacuum cleaner cleaned it all up without any issues! The farmer's wife was delighted and bought one right there!
The moral of the story is: If at first you don't suck seed, try drier grain.