Vern Blosum does not exist. The story can be told simply: in 1961 an artist paints five canvases inspired by pages in a horticulture book; then came parking meters, water hydrants, and animals. Some of them were shown at Leo Castelli Gallery, sold to collectors and public institutions, included in seminal exhibitions or books on Pop art--a seemingly normal progression in an artist's career, were it not for a rumor that emerged regarding his true identity. Alfred H. Barr, the legendary director of MoMA, started to worry about the rumor sometime in 1964 and, after extensive inquiries, came to...