Well, I don't know why a PK prey item would ever be TOO warm since you give it to the snake just after it dies and there's still natural warmth in it. FT, though, could be potentially overheated.

The only time I would think overheated food would cause a negative feeding response would be if it were cooked...which should never be done anyway, or came in direct contact with a very hot surface. Since both of those are "unnatural", the snake would most likely ignore or pull away from that prey item. Just my supposition...