Wikipedia has an answer to this, the gist of which is that all of the 1923 copies were bought back by someone aiming to do a remake, and stored. Unfortunately the building they were in was destroyed by fire, and that's why you can't find copies anywhere now.
Here's the long version:- " The film was an adaptation of a novel whose previous screen adaptation was completed for release in 1923, but it is the earliest surviving adaptation.
In 1928, Herbert Wilcox acquired the motion picture rights to the novel from I.W. Schlesinger to produce a remake. To eliminate competition with his film, Wilcox purchased all existing prints of the 1923 adaptation. Approximately one year later, he officially announced the inclusion of this project in his portfolio of motion pictures in production.[3][4] He planned to film it in multiple-language versions in French and Spanish,[5] in 2-strip Technicolor, and with a full libretto of native music.[6] The project was abandoned due to the Great Depression, and was not restarted until 1935, now with backing from the newly formed General Film Distributors (GFD). After development resumed, Wilcox planned to cast either Joel McCrea or Richard Cromwell as the male lead. It was going to be shot in 3-strip Technicolor in Honolulu.[7] [8] [9]
After a spectacular fire at the British and Dominions Imperial Studios on 9 February 1936 destroyed the last surviving print of the 1923 film, Wilcox lost interest in the project, though, and the rights were assumed by GFD's new sister company Gainsborough Pictures at the recommendation of Frank Launder, who always admired the novel.[10] Gainsborough announced the film in 1938 as part of a slate of 10 films.[11] The stars were to be Michael Redgrave and Margaret Lockwood, who had just appeared in Gainsborough's The Lady Vanishes; Will Fyffe was to co-star.[12][13] Carol Reed was considered to direct.[14][15] In 1939, Gainsborough went into a co-production with 20th Century Fox to secure funding, and Lockwood was going to co-star with Richard Greene, under contract to Fox.[16] Plans to make the film were postponed due to World War II.[17]
The project was reactivated after the war and announced in 1946, with Frank Launder attached to direct.[18] Extensive location searches were undertaken before deciding to make the film in Fiji.[19]
Plans to make the film were postponed due to Britain's currency difficulties, but eventually, plans were reactivated"
My grandfather was a builder in Fiji, and he was in charge of building the sets for the 1949 version. My 95 year old mother tells me he said the actors were all very nice people, and he enjoyed his time working for them.