In 1939, while preparing to fight his right to attend the segregated University of Missouri to practice law, Lloyd Gaines steps out to buy stamps on a cold rainy night and is never seen again.

Sources: 

https://en.wikipedia.org/wiki/Lloyd_L._Gaines 

https://calendar.eji.org/racial-injustice/mar/19 

https://scholarship.law.missouri.edu/gaines/ 

https://historicmissourians.shsmo.org/?page_id=6877 

https://www.riverfronttimes.com/news/the-mystery-of-lloyd-gaines-2479115 

 https://www.kbia.org/education/2018-12-12/legacy-of-missing-lloyd-gaines-1938-supreme-court-plaintiff-still-haunts-higher-education