I usually don't check, because they rush you to leave the drive thru and people behind you get POed so I just go once I get it.
Myself, I am in no way a confrontational person, so if they dont put somthing in the bag I just say " those b@stards!..." and move on.
But my mother...oh no, she is a different story!
She calls, she complians, she makes me go ALL the way back to the place to get what we ordered again. Her thoughts are the same as most " if I paid for it I want it!"
Which I agree but I am just not one to confront, you know.
So now I make sure I check all the bags BEFORE I get home!