Also, the temperature of separate packs isn't additive. Multiple packs won't cause the package temp to somehow raise above 100-115*. The only thing that adding multiple packs will do is cause the package temperature to reach 100-115* faster, and resist the external temperature longer. You will also definitely need that humidity bag you talked about, since that heat can really dry out a plant.
Mass: Since I do ship a lot of Neps around the country, I'm interested in how a heat pack did that to your plant. That looks a lot like frost-burn, but I've never seen what cooking a plant looks like. Was the plant sealed to keep from drying-out?