I found this same file name in my 404 log yesterday, and did a search on that name. I got no results at all. After reading this, I did the search again and got several results, but I'm not sure that I got the insight.
Is this just Google doing a random check to see what happens? That's the closest thing I could find to an explanation.
Google does often test sites with page names designed to deliver a 404 response to see how your server handle the 404 response.
Some sites return a 200 OK with some other page, typically the home page, to stop visitor bounce and Google identifies this so it doesn't index the same page multiple times and possible make the wrong page supplemental.