From https://en.wikipedia.org/wiki/Jack_in_the_Box_(Satie)
"... after he wrote the piano score, he lost it some time after 1905. [composer Erik] Satie believed it had gone missing on a bus and that it would never be found, but after his death [in 1925 -- twenty years later!] it was found in his squalid apartment in Arcueil (some sources say it was hidden inside a notebook lodged down the back of his decrepit piano) ..."