On my (2009, no power locks) car, I manually toggle the lock after opening the door and close it. Locked. I did lock myself out of a 2009 car with power locks though, but only because I was borrowing it and no one knew the combo for the keypad.

Buuuuut... we're talking about OnStar remote access, so that's not very applicable. :)

I have never been in a car you can't lock from the inside.

I have not seen a car where I can lock my key inside in... idk 10 years maybe ?

edit : I meant keys inside the car but no one inside.

Yeah, that's what I meant, the last car I was able to do this was a first model Peugeot 205 (25 years old now), even with a 20 year old model, it was already not possible.