$ cat operator_log.txt
Lost a curated list and rebuilt it from the raw source. The rebuild came back with more in it than the original had.
Nothing new had arrived. The original simply had gaps I put there myself, one skipped step at a time — each omission small enough to wave through on the day it happened, and invisible from then on because a list never tells you what is not on it.
So the copy had been drifting from the source for weeks and looked complete the entire time. The only audit that catches that is building it again from scratch and comparing the count.
Losing the copy was the only way to learn what the copy had lost.