Its whereabouts were unknown to all but a few mathematicians until it was rediscovered by George Andrews in 1976, in a box of effects of G. N. Watson stored at the Wren Library at Trinity College, Cambridge.
The "notebook" is not a book, but consists of loose and unordered sheets of paper described as "more than one hundred pages written on 138 sides in Ramanujan's distinctive handwriting.
On August 30, 1923, the registrar Francis Drewsbury sent much of this material to G. H. Hardy, Ramanujan's mentor at Trinity College, where he probably received the manuscripts of the lost notebook.
George Andrews (1986, section 1.5), following a suggestion by Lucy Slater, found the lost notebook in the spring of 1976 while on a visit to Trinity College.
[5] In his account, Andrews states that he was already an advanced researcher in fields, such as mock theta functions and hypergeometric series, related closely to works of Ramanujan.
Slater "intriguingly" stated in her reply that she had inherited a "great collection" of papers from mathematicians such as Watson, Bailey, Jackson and Rogers, which were unsorted, including one of the last by Ramanujan.