Whatever the circumstances, it appears that a method not unlike Sherman’s flash lab was being used in England as early as 1908-12.
According to British art educator Marion Richardson, it was originated by her drawing teacher, Robert Catterson-Smith, the headmaster at the Birmingham School of Art. As noted by Arthur D. Efland in A History of Art Education (NY: Columbia University Teachers College Press, 1990),
“Smith would show lantern slides to his students for a few moments, after which the image would be withdrawn. Richardson [in her autobiography] described the process further: ‘We closed our eyes and, keeping closed, quickly outlined the picture. This “shut-eye” drawing was perhaps Mr. Catterson-Smith’s greatest contribution to art education.’”