That's really unfortunate. If it's not too much trouble, could you post a pic of the overheated box and heat pack?

I usually try to ship on the cool side. I received one shipment of snakes that was delayed in an unheated cargo hold of a plane, and at first I thought they were dead because they were nearly frozen. However, they eventually warmed up and all of them survived.

On the flip side, I've also heard of a lot of snakes dying because of being overheated during shipping.