nseah, thanks for the feedback! I just remembered that I did leave the seats down (nothing in the back of the car, no weight on the seat) for a week. Too lazy to put them back up i guess. Maybe leaving them down for a week caused the indents.
Regardless of whether this caused it or not, it is still a design flaw. I'm going to try the pipe insulation suggestion. I think i have some leftover from when I wrapped my house's pipes.