@UltikanaRe I'm not disagreeing that not seeing it was my fault - I thought for some reason that it was zooming in much more than it actually was, so the area kind of hid in plain sight - I wasn't looking for big areas, so I overlooked it. That was my fault, and I won't deny that.
Furthermore, what I said prior to the GM stepping in was:
I notice that the area circled on your nation sheet doesn't exist on the map you gave. One of the two is out of date, you should probably fix that ^^
And after that,
Let me rephrase. The "Aeride Sea", present on your nation sheet, is nonexistent on the full map.
Both were nothing close to "calling you out", and my statement that the "Aeride Sea" doesn't exist on the full map was 100% accurate. All you had to say from the beginning was that it was a subsea of Tyon, and that would have been the end of it. Instead you said you used a blank map on purpose, without actually pointing out where your empire was located. Due to my oversight (again, my fault), and the fact that you didn't actually point it out, it wasn't unreasonable to suggest that it wasn't there - and the GM didn't make any attempt to show where it was, either. I won't say either of you were at fault for my failure to see the area, but I'd be lying if I said that a simple, proper explanation wouldn't have ended the argument before it began.
Also, that took me over an hour to label and I am not redoing it.
You'll notice that I offered to redo the map myself, to resolve all the issues presented by the map generator's faults. I'd even maintain it with up-to-date political borders, to avoid the same confusion that started this argument in the future.