The story of the first movement’s origins has all the makings of a whodunnit: during Bach’s lifetime, the score was neatly and systematically severed from a larger sheet (containing the Harpsichord Concerto BWV 1062) after bar 62. But why and by whom? Though a replacement sheet must have existed, it has been irretrievably lost. Thus the missing ca. 46 bars have been reconstructed with varying degrees of accuracy in all previous editions, and sometimes the movement was even entirely omitted. Barthold "Sherlock" Kuijken found traces of the flute part - chiefly slurs but also a few high notes - in the remaining autograph of BWV 1062. He has modeled his version along these clues in an attempt to approximat e Bach’s original form as closely as possible.

"I am very, very impressed by the Breitkopf / Kuijken edition of Bach's flute sonatas that I bought yet another copy when I discovered to my horror that I was en route to a recital abroad without my music. Breitkopf (make sure it's the new edition by Barthold Kuijken you buy) publish each sonata separately,  which inevitably works out more expensive, but with the amount of extra information and inclusion of flute and bass parts together this is a bargain. Everyone should have these, even if they already possess other editions." (Pan Magazine)