Riot made me lose my 1st place

I had this one game in TFT, where I earlier beat the first place dude. When I face him again I noticed that at the end my level 3 Braum who had the 83% magic resistance, Warmogs, and GA was fighting a level 2 Veigar with no items. I still had my GA to use, but then all of a sudden, the game just said I lost and I got placed 3rd place. I feel like the game cheated me. I think that is a bug. The game was supposed to keep going.