Grateful Dead and Woodstock

Heard one recently and wanted to ask the masses here since some of us are old enough to have been around then and there might also be DeadHeads here: The Dead performed at the original Woodstock Music & Arts Festival but because of performing conditions they had all references to their having been there removed? Something about the stage setup and electrical grounding and Bob Weir getting knocked on his butt when he went to sing, got too close to the mic, lips touched the mic, shock happened and he got floored. There might have been other things going on as well, but that's what I remember from the story.

True or just myth? I would think there were all kinds of possible electrical problems going on there considering the weather and transitory nature of the whole deal.

That's my one life's regret: I had tickets to go but didn't and I never saved the tix as a souvenir.