First, Happy Father’s Day to any jazz loving Dads out there!
pryso, sometimes we forget that great artists are people too just like all of us and are subject to forgetfulness and other similar issues just as we all are. I would be willing to bet that this “lost” Trane recording is not the only one out there that has been forgotten about. Musicians would often (and still do) go into the studio and lay down tracks that would eventually find their way onto record releases without prior concrete plans to do so; or would go into the studio to rehearse and the engineer would simply roll the tape. No big money to be sure, but those guys were very busy; not just recording, but with tours and other live performances. The truth is that most (not all) jazz artists were notorious for being disorganized with their business dealings. Re my comments re the record label:
Impulse was a relatively small record label with very limited resources. The more records they released, the more that their limited resources were taxed and the more likely that a tape might be lost. Much more unlikely that, as with a label like Columbia, would they have an archivist on staff. So....
You may find this of interest:
http://www.billholland.net/words/Labels%20Strive%20to%20Rectify%20Past%20Archival%20Problems.pdf