Speaking of people who dropped off the face of the earth, Bobbie Gentry released her last album in 1970, when she was only 26. She continued knocking around show business for a while, without a great deal of visibility; her final appearance in the public eye was on "The Tonight Show" on Christmas Night, 1978.
I wonder if they had a hard time finding guests to appear on "The Tonight Show" on Christmas. I'd bet money that Johnny turned the desk over to a guest host that night, which means that Bobbie Gentry's showbiz farewell would have come at the hands of Joe Garagiola or Roy Clark. If anyone has the means to figure out who was hosting that night, please let me know.
Bobbie did marry Jim "Spiders and Snakes" Stafford in 1979, but that lasted about as long as Stafford's hitmaking career.