When Loki and Thor first meet up on Sakaar, Loki reveals that he's been there for weeks and yet despite this, Loki is somehow completely unaware that Hulk is also on Sakaar as shown by his reaction in the battle arena. This seems incredibly unlikely considering that not only is Hulk a huge celebrity there, but also that Loki had gotten in good graces with the Grandmaster. Surely he would have found out who the champion is. His likeness is even featured atop the Grandmaster's tower.