The first incident of note involving a remote mic left on happened on Broadway around 1962. Those mics were rarely used until the 80s. Actress Anna Maria Alberghetti was staring in the sell out Broadway show “Carnival!” Once her scene was done she went to the bathroom forgetting that her mic was still on. So she does her business with the crowd hearing every noise that goes with it. The house was all laughing once they figured out the source of the unknown sounds. She came back out for her next scene and got a standing ovation.