Background: Nehemiah Curtis "Skip" James (June 9, 1902 - October 3, 1969) was an American Delta blues singer, guitarist, pianist and songwriter. His guitar playing is noted for its dark, minor-key sound, played in an open D-minor tuning with an intricate fingerpicking technique. James first recorded for Paramount Records in 1931, but these recordings sold poorly, having been released during the Great Depression, and he drifted into obscurity. After a long absence from the public eye, James was "rediscovered" in 1964 by blues enthusiasts, helping further the blues and folk music revival of the 1950s and early 1960s.
Context: For the next thirty years, James recorded nothing and performed sporadically. He was virtually unknown to listeners until about 1960. In 1964, blues enthusiasts John Fahey, Bill Barth, and Henry Vestine found him in a hospital in Tunica, Mississippi. According to Calt, the "rediscovery" of both James and Son House at virtually the same time was the start of the blues revival in the United States. In July 1964 James and other rediscovered musicians appeared at the Newport Folk Festival. Several photographs by the blues promoter Dick Waterman captured this performance, James's first in over 30 years. After that James recorded for Takoma Records, Melodeon Records, and Vanguard Records and performed at various engagements until his death in 1969.  More of James's recordings have been available since his death than were available during his lifetime. His 1931 recordings and several of his recordings and concerts from the 1960s have been reissued on numerous compact discs, in and out of print. His songs were not initially recorded as frequently as those of other rediscovered blues musicians. However, the British rock band Cream recorded "I'm So Glad", providing James with the only windfall of his career. Subsequently, Cream's adaptation was recorded by other groups. James' "22-20" inspired for the name for the English group 22-20s and the British post-rock band Hope of the States released a song partially about the life of James, entitled "Nehemiah", which reached number 30 on the UK Singles Chart.  In 2004, Wim Wenders directed the film The Soul of a Man (the second part of The Blues, a series produced by Martin Scorsese), focusing on the music of Blind Willie Johnson, J.B. Lenoir and James. Because James had not been not filmed before the 1960s, Keith B. Brown played the part of the young James in the documentary.
Question: when was he redicovered?

Answer:
He was virtually unknown to listeners until about 1960.