I strongly suspect I saw this happen in realtime in late 2013 and early 2014 when Snowden's documents were being disclosed every few weeks by The Guardian, The Washington Post, Der Spiegel, etc.
I was curious how the story was being reported on and interpreted by the traditional (non-technical) media. I wanted a general sense of how well the "slow drip" strategy was working, if the original disclosures were being reported on with a reasonable accuracy, or even if anybody even cared at all. For about 8-10-ish months I made a habit of spending a few minutes each morning skimming the results of basic searches for "nsa", "snowden", etc on Google's main search as a simple /search?q=$term request, and again with the "Past 24 hours" and "Past week" features. I would also check the same search terms on Google News.
Most of the time it there were no surprises: e.g. The Post publishes an important document from Snowden's archive in a detailed article that attempts to explain the underlying tech to a general audience. The other large players in the traditional media quickly followup with articles that add a layer of indirection, cut out all the technical explanations that don't fit into a sound byte. It didn't take long for that process to devolve into lots of clickbait headlines for articles that generally lacked technical - or legal - details. My point here is that this process generally followed a fairly consistent process as the original disclosure diffused into clickbait.
However, on two (perhaps three?) occasions, I noticed a story still early in that process. I know at least one of those involved Google specifically. While chasing pointers back to the original disclosure article and opening a new browser window for for the usual test searches, I noticed Firefox was becoming annoyingly slow and leaking memory like it always did. After restarting the browser and reloading the test searches... every trace of the story was gone. The articles themselves became 404s a few minutes/hours later.
Unfortunately, I have no useful evidence. I was "just" informally skimming headlines to get a general sense of the reporting, so by the time I finally realized I should have been recording everything I had already missed the interesting stuff. It's hearsay, but I am very certain I saw articles suddenly vanish from Google search and Google news after restarting Firefox and pressing F5 on several tabs.