If you're at a top-tier research institution, you'll often hear that there are privately funded research that are sometimes decades ahead of the mainstream, be it in the medical sciences, computing or some other fields.
Just this week I came across two papers on unsupervised learning written 20 years ago that resembled some "novel" techniques developed by Microsoft Research in 2019.
Have you ever come across "secret/unpublished research" of note, anecdotal or otherwise?