I had seats in the first few rows of section LL and used to see a lot of it get tossed off the upper deck. It was really common then just sort of went away, not sure why. My guess is maybe the university put a stop to it because the lower deck was complaining. It was happening when I was a student in the mid 80's so I don't know when it started.
Another lost tradition was the orange helium balloons that got released by the crowd at the start of the games. Think that ended in the late 80's.
I thought you might have better chance to see it on some of the old highlight videos from back in the day, not sure now much the TV crews caught things like that for the broadcasts and in the pre-cell phone era, your not going to see anyone in the crowd recording it.