Rear seat problem

Ok... so I'm new, old and easily confused. But I've had experience with Prius so finally, as what I hope will be my last car, I bought a used 2011. And I love it

BUT

While I can fold down the 60% side of the rear seat, the 40% is immobile. There is no latch or obvious way to release the seat. My theory is that something happened to the original seat and the previous owner had thi9s one replaced or Toyota offered this option or the latch is hidden somewhere. As I bought the car at auction, I was concerned about other things and never checked the seat.
Anyone have any ideas. (I know about what I should have - question is what do it do - if anything) Thanks