Here is the deal: this show was originally scheduled for August 20, 1969, but was rained out and re-scheduled for the next day. There is clear and overwhelming evidence, from multiple independent data streams, that this is exactly what happened. See entry at Lost Live Dead and follow the many links from there for more evidence. For the smoking gun, there's this: Carole Beers, "No Show: Ungrateful Clamor Didn't Rouse the Dead," Seattle Times, August 21, 1969, page illegible.