Cargo cover on premium?

Mine came in a flat black fabric bag that was in the back, along with the charger cable. For models less than Advanced, this is a light weight twist-spring-edged "D" shaped piece of fabric. It has two loops that hook near the seats and two strings that hook on the rear hatch. For about $400, you can buy an aftermarket matching heavy duty tonneau cover, like the ones in older Prius models. Its like one of those twist-to-close windshield thingies.

Ask the dealer. Perhaps they didn't understand what it was when they prep'd the car. Heck, I had to remind my dealership that they should charge the car before I picked it up.

 

Tonneau cover not so bad. Give it a try, you might like it.
I have a premium and was very frustrated with the idea of a tonneau cover at first. I owned a gen 3 for 10 years and found the solid cover to be indispensable. In conferring with the dealer and looking at the attachment area in the premium, it's not clear the heavy cover will work on anything but the advanced. After it sitting in my garage in the carrying sack for a week, I finally decided to try the new one (change is difficult for us humans).
After getting it in right (you have to have the longer cords hook to the top of the lift back or it otherwise blocks the lower portion of your rear view), I actually like it better in some ways.
Contrary to some comments, it's not see-through so it conceals what's there. It also lifts up automatically when you open the lid as it's hooked to the underside of the lift gate. Because it's fabric, it also has the ability to flex and cover the contour of some over-sized objects that the heavy cover couldn't accommodate, requiring you to just leave it open.

What I don't like about it - it's cumbersome to take off and store. I also don't like the fact that the space at the very end of the raised battery area with the little cover that pops off is specifically designed for stowing away the hard cover of the advanced model. Pretty much a wasted area if you don't have what goes there. It's like having sections of the Entune system come across your screen that you can't use or even pay to upgrade to - why have them there ?(I suppose that's another thread).