Warnings problems of the 2017 Lexus RX

I was sitting at a complete stop for more than 45 minutes behind a fatality accident on the highway they had closed while occasionally removing foot from brake to inch forward a few feet a best and then stop again never touching the accelerator when I realized at one point traffic beside me was moving, I thought, it was my Rx 350 while pressing brake all the way to the floor with no resistance I attempted to put the car in neutral to see if it was slow me down as an upcoming crash was unavoidable. No brake assist, precollison warning or assist, no emergency braking, no resistance from brake pedal and ** warning lights came on at all prior to impact with the back of a stopped semi truck** and during the entire incident the speedometer remained at zero or moved a tiny bit off of zero as if it was pulsing somehow and the accelerator was never touched while car felt like I was being pushed from behind, randomly accelerating on its own before impact.