Now this is weird - car started with nobody in it

What else do you need to do besides press the power button, set the parking brake and (if desired) turn on the charging timer? To me it's actually less complicated than turning off a manual car with mechanical keys...

 

Old-school keys are more fool-proof though, not that I'm enamoured with them. But for example: you've got a traditional car key, and it's on a ring with your house key. There's no way to get into your house and leave the car running.

 

Arrive home. Position vehicle in usual "landing pad" position.
1. Press park button.
2. Press parking brake.
3. Shutdown life support systems (noting sound of compressor spooling down).
4. Scan Dashboard for propulsion system status.
5. Note HV battery status on MFD.
6. While propulsion is still enabled, listen for unusual sounds from battery cooling fan.
7. Disconnect Dash Cam cable and stow.
8. Detach Dash Cam from windshield and stow.
9. Initiate MASES (Main And Secondary Engine Shutdown), noting HV power bus disconnection sound from rear compartment.
10. Deactivate vehicle access / egress security locks.
11. Disembark from vehicle.
12. Fold drivers mirror.
13. Initiate walk around check of exterior fuselage, moving anti-clockwise around the vehicle. (UK vehicle).
14. Check under the propulsion unit area for possible coolant or vital fluid leaks.
15. Fold passenger side mirror.
16. Open cargo bay door.
17. Slide back cargo bay radiation shield.
18. Retrieve work equipment from cargo bay.
19. Return cargo bay radiation shield to active position.
20. Close the cargo bay door.
21. Manual check to confirm cargo bay door is locked down.
22. Activate vehicle access security shield (double lock protocol).
23. Last visual check of vehicle as you walk away.
24. Note final automated shutdown sequence noises from vehicle as you retreat.
25. One last vehicle observation from the bedroom window...

I did say it was "Big Bang Theory" OCD style



iPhone 6s +

 

I'm worried that the OP's Prius may have started itself up and kidnapped him, and is now holding him for ransom in an undisclosed location - he hasn't been heard from in almost six weeks.