I had a very similar incident.
After purely dominating the game and pushing both towers/inhibs, controlling every dragon...their team (Teemo/Nasus/Brand) were able to prevent us from getting the tower. Nasus would slow us to a crawl and Brand and Teemo would just lay into us while standing at the safety of their fountain.
After going on for over an hour, in which they hadn't left their fountain for over 30 straight minutes....we got frustrated and lost. Because at that point I wanted to get out of the game more than I wanted the win.
Tldr - If the turret was on the other side of the nexus, that game would have ended 20 minutes in and the team that deserved the win would have gotten it.