What I’ve done in the past is to copy the URL of the unavailable video (if it’s still accessible via the playlist entry, sometimes it isn’t which is annoying) and feed it into the Wayback Machine in the hopes that it got archived at some point. The video stream isn’t usually available that way, but at least the page title sometimes is, and then I can search for other versions of it.
That depends who gets infected.
You or me infected by malware? No thanks!
Egon Mark infected by malware? Absolute hilarity!