Maybe I have no understanding of what a binary search is. My understanding is that you check halfway through the video, see if the thing has happened yet, then skip halfway to the end if it hasn’t. Check again, skip again. When you see the cue that the event has happened, you rewind to halfway between the latest point where the event hadn’t happened yet and the earliest point when it has. Keep doing that and you can pinpoint the exact frame where the event happens in a matter of minutes.
Binary search would be largely useless in cases where you have a good chance of skipping right past the event. If the video is an hour long, and the event happens 34 minutes in and leaves a visual cue that lasts less than 11 minutes, then binary search does not find the event. At that point, watching the video fast forwarded would be the way to go, and that’s not a binary search, that’s just watching the video.
So I should correct myself: the visual cue doesn’t have to last the remainder of the video, it just needs to last until one of the points that you check. Which still makes it not useful for things that don’t leave visual cues that last more than a few minutes, because it cannot find most of those events if they happen at a random time in an hour+ video.