I haven't read the paper either but billions upon billions of organisms constantly have some tiny chance of ending up in the conditions where they fossilize and

I haven't read the paper either but billions upon billions of organisms constantly have some tiny chance of ending up in the conditions where they fossilize and could later be found. A few thousand or million exposed structures over the few-thousand-year lifetime of a civilization is, in comparison, a microscopically smaller chance of preservation. Nature, in contrast, gets effectively infinite shots at this, the fossils record still has gaps that dwarf the lifespan of human civilization as it is.