You can get a Gatomon early in Dusk by digiconverting a Pawnchessmon W from Thriller Ruins, and degenerating it to Puttimon (for whatever reason, they forgot to make befriending Puttimon a requirement for Pawnchessmon W to degenerate to it). You should then be able to take it up Gatomon's digivolution line. You should also be able to find wild Angewomon in Highlight Heaven, provided you're far enough into the game ( and I do mean like really close to the end of the game, you unlock Highlight Heaven way late in Dusk).
It would appear that I have been driven to madness. Probably would have been faster to walk.
Like practically as soon as you start the game really. I don't really think they forgot exactly so much as they realized Gatomon is a VERY popular Digimon, and they'd have a lot of angry Dusk owners if they had to have access to WiFi just to get her. PawnChessmon white and black should both appear there from the start, there's no quest requirements for them. Though it might take a while to get enough scan data at first because of how little you get per scan until you get your rank up and how few Digimon will appear at once initially.