I guess you would have to get in the habit of closing the door without touching the outside handle. I am trying to remember what part of the door I touch when closing it -- probably the handle.
I have only had my car for two days but was having problems locking up. Finally I went around and opened all the doors (and hatch) and shut them "good" and it locked. A little trial and error and I discovered that the hatch needs a solid "slam" to fully latch. It's now on the list of things to have checked next time I am at the dealer. Bob
I had the same problem and mine was caused by pulling the hatch down using the "grab here" handle. I didn't want to pull so hard that it shut on my hand and I didn't want to slam it -- it would barely latch or look latched but not have gone all the way. Now I just pull it down far enough to bring the Toyota logo even with my chest and then push the hatch down with my palm on the logo. Works fine.
Well, that makes me wonder if it locked them automatically because you never actually closed the door after unlocking them. Or perhaps some other complex series of events where the car is outsmarting itself. To check for sure, I would actually try shutting the car off, opening the door, locking from the switch, getting out and closing the door. (In other words, to exactly duplicate the real-world scenario.)
Here's a source for the hatch handle I use: SAAB Trunk Handle for BMW - Ultimate Cupholders - Cup holders for 5 Series and 7 Series BMW, Z4, Porsche Boxster / Porsche 911 996, Mercedes, Audi, Acura NSX and other fine cars. The ultimate cup holder / cupholder! This makes it much easier to close the hatch. And here's a note about the way I installed it: PriusOnline.com • View topic - Installing the hatch handle After a little while I decided I wasn't happy with the nylon caps for the screw head and stuck two fat pieces of closed-cell foam tape to the car to cushion them. After four years there' no harm to the paint.
Even if, for some reason, the key fob is not in your pocket and was left inside the car and you use the door arm rest rocker switch to lock the doors, the car will just immediately unlock the doors again. It looks out for us!