I had a similar experience about 8 years ago in Intro to Linear Algebra. I had been attending lectures at my school but I ended up missing a day so I decided to find the corresponding lecture from MIT. It turns out, I was able to watch a lecture from the author of the textbook we were using. Even crazier, the lecture I watched online ended with him working through an example problem but he did not finish.

When I went to the next class in person, our professor was finishing up the exact same example problem from the lecture video. It could have just been coincidence that that exact lecture lined up the way it did, but it kind of opened my eyes to how silly it was to have professors repeating the same thing year after year.