If you searching just on the Internet then you are missing around 50 years of history of networking and software in general.
Unfortunately, the internet is the only resource I have readily accessible.
One more avenue for search is to look at the nearby code, not just strictly IRC-related. There were multiple methods used to discover node's own external IPv4 address. Those also aren't all invented by Satoshi, but borrowed/copied from the pre-existing code. Those were the other things that tended to trigger false-positives.
There are indeed several methods used to discover a node's external IPv4 address, but I expect any engineer who has used sockets before would be able to write them. I have found no reason to think they were copied from anywhere. It's odd that they would trigger false-positives. [https://github.com/trottier/original-bitcoin/blob/92ee8d9a994391d148733da77e2bbc2f4acc43cd/src/net.cpp]
Are you a CS history researcher associated with an accredited university? Because if you are really into history of CS I may be able to put you in touch with people who may be willing to donate their personal archives fairly soon. But you would really need to be able to read obsolete media like open-reel magnetic tapes or U-Matic and SVHS video cassettes with PAL/SECAM color.
Sadly, I am not. Just a curious software engineer.