How did Mr. Drysdale find out about the oil and the Hillbillies?

Mr.Drysdale's bank was the one Mr.Brewster (who had bought the oil swamp for $25,000,000.00) arranged to have the money go to.Mr.Drysdale was thrilled to have so much money in his bank...and he arranged a big welcome at the mansion next to his.But he heard that the mansion was being invaded by vandals and rushed down to see them in jail. He grabbed the tall older man's shirt and said,"What have you done with J.D.Clampett?" The reply;"I'm Jed Clampett and I'd apreciate it if you'd let go of my Sunday shirt."

and when he had them brought back to the mansion, they thought he was bringing them to prison.

Loved that first episode.