Sentence:  But then , after the little operetta had been given its feeble amateur rendering , everyone insisted that it was too good to be <WSD>lost</WSD> forever , and that the Royal Academy of Music must now have the manuscript in order to give it the really first-rate performance it merited . 
Meaning of the word marked with <WSD> tags:  no longer in your possession or control; unable to be found or recovered