Before you get too worried, take a look at your setup menu either in the cluster on a low line truck, or in the radio under APPS on a high line truck and make sure they didn't default to off. If that isn't it part of the TSB involves downloading the vehicle configuration that was built in error without the heater being turned on. The configuration is the master set of instructions the vehicle controllers use to make everything work properly. The TSB also asks the technician to save or print the configuration before and after the flash so concerns just like these can be identified easily. So I would contact your dealer promptly and ask them if they followed the TSB and saved the data. By comparing the two they will see the bit that was missed and can contact the factory to correct it. The fix is correcting the data and then restoring the vehicle configuration again from the mainframe.