Not sure if that was the sole thing that cost the game (given the gold margin, champion deaths and turrets that had fallen) but I would guess that it was a factor. I just measured the distance of the hooked champ from the edge of Thresh's hook in your replay and I am deducing that the champ's boundary just barely touched the edge of the hook's boundary. For a few of the champions, the boundary around the champion is a bit on the large side (here, I'm guessing the devs did it to accommodate her rifle). If it was another champion, then the hook could have easily snagged the minion - not the Caitlyn.
(A similar problem exists for the Lux ult.)