It has never occurred. I can hear what the person is saying, but if all we needed was to hear what people are saying, why would we need visuals? It is important to remember visuals are there for a reason.
I don't know when it has, and I've never had it happen. I've been to several debates in my community, and I've never once been provided information in Braille or in an electronic format that I could take home and read.