Bug was clearly part of the lexicon already. Otherwise no one would have written "First actual case of bug being found." And it wouldn't have been so funny.
Pedant "debunking" obvious joke in a JSTOR article is pretty funny in its own right, though. I hope Matthew Wills will explain how chickens don't cross roads next!
Grace Hopper joked about finding a literal bug, because "bug" was already a term for a defect at the time. It it weren't, the joke wouldn't make sense. There seems to be widespread confusion about that, leading to people to write "debunking" stories every couple of years.
I mean, the sentence "The first actual case of a bug being found" implies that "bug" was already being used in the context of a malfunctioning computer. Otherwise, why would they write it?
Debunking of the bug story as etymological folklore has been going on since at least 1984. Every few years there's another article about it (which is good for the daily 10,000.) The first appears to have been in Byte magazine and then IEEE Annals of the History of Computing in 1984. Followed by American Speech in 1987 and again in IEEE Annals of the History of Computing in 1998.
Links: https://archive.org/details/eu_BYTE-1984-07_OCR/page/n33/mod... https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=4640793 https://doi.org/10.2307/455415 http://ivizlab.sfu.ca/arya/Papers/IEEE/HTML%20Docs/Computer%...