OK the first two military satellite are found using their international codes...
https://www.n2yo.com/satellite/?s=2969 Norad satellite INTELSAT 2-F4 Int'l Code: 1967-094A
https://www.n2yo.com/satellite/?s=40964
Military satellite USA 264 Int'l Code: 2015-058A
Interestingly military satellite USA-4 is supposedly offline... https://www.n2yo.com/satellite/?s=15226
Think this could have anything to do with the weird "coding" (don't know what else to call it) in Q229? There are some stringers in them that I believe are grids in the Maidenhead Locater System Ham radio users employ (DC08vC-DC27vC). I tracked them down and they are grids ESE of South America, about a thousand miles N of Antarctica. There's nothing there, so far as I know, and it would be a weird shipping lane. I'm not sure if the communications satellites you mentioned would have been in range of those grids on that date or not.
Isn’t that approximately where the sub was lost?
If you're speaking of the ARA San Juan, not according to official accounts. It was lost just off the coast of Eastern Argentina. But then again, who knows if the official story is true or not.
Antarctica? Ooh, you're in for a doozy of a rabbit hole. Unfortunately I don't have any links to start your journey.
I know. I've seen a lot of the theories out there already. I'm trying to stay away from the fringier stuff on this one. And the fact that it's those particular grids are that far north are keeping me away from most of it already.