I do know that on my 2015 model the heat shield is bigger covering most of the area under the bed. Not sure if anyone else on here has a 2018 model to compare to...so go back to your dealer and complain. It should still be under warranty. I use mine to haul out the trash each week, I normally go for a little ride then back to haul trash, never had a plastic bag melt of even feel hot, even after 20 minutes of riding. Your dealer should know and be able to add another heat shield if one is missing