I wanted to look up a reference I'd cited some years ago, and tried to "google" for it. Nothing.
DuckDuckgo had it.
It wasn't something that should have triggered google's "badthink" algorithms--and I've seen this more than once.
Maybe anything bloggy that's older than X years gets dropped, or older than X years and blogger says it hasn't been accessed in Y years. I've searched for odd things sometimes and run into tiny old blog sites, so I'm not sure that hypothesis works.