Knowing that the car rolled I would also think that at between 4:20 and 5:30 (when vehicle was found) that it was pretty dark and since the car rolled Bryce's belongings would be all over the car (cell phone, laptop, wallet etc) and ones instinct would tell you to get out of the car, so that might be why everything was left in the car - he couldn't find anything on the way out. The police found everything but they have flashlights and it was probably getting light from 5:30 on, and they weren't in a hurry to exit a vehicle that just rolled
I know from my own experience that yes first thought is to get out of the vehicle when rolled.
We are assuming that Bryce was in the car because the k-9 unit tracked his scent, right? The back window was broken out not in and with a tool that Bryce knew about.
Have they confirmed anything about the blood found inside?