Not even that. The author already knew the bug was there, and fed the LLM just the files related to the bug, with the explanation on how the methods worked and where to search, and even then, only 1 out of 100 times did it find the bug.
There are two bugs in the article: one the author previously knew about and was trying to rediscover as an exploration as well as a second the author did not know about and stumbled into. The second bug is novel, and is what makes the blog post interesting.