Sounds like BS to me. call Chrysler cares and let them know what is going on. Warranty work done at a dealer under warranty should be covered at any dealer under warranty. Sounds to me like they probably won't be able to bill for their time since it was another dealers fault. Not your problem. Whenever they move up a part numbers letter designation it is usually because something has been modified. Maybe there was an issue with the Hybrid that initiated the Themostat needing to be revised??