That row of openings right above the mouth and below the eyes on the snake's face.....those are heat pits. They ARE heat sensitive when it comes to hunting. They use smell and heat to find their prey.
Also, it's critical that the snake not eat a partially frozen mouse, or even one that is thawed but still really chilled in the middle. Frozen or really cold meat can make them very sick.
I don't think it matters where in the enclosure you place the prey item. But if you find a spot that seems to work best, then use it. If the "hot spot" is "too hot" for any reason, then it's too hot for your snake as well. How are you heating and how are you measuring the temps?