problem myself) some of the locks on the Z were faulty and shut by themselves for no apparent reason. Mine do this all the time and I also have an aftermarket alarm that "technically" should prohibit that from happening. Ive gotten into the habit of always opening my drivers side window about 2 inches if I ever need to get out of the car to get something, that way if it locks (and it usually does) I just reach in and open the doors.
Do what you feel is right, because at the end of the day nobody gives a shit.