When my DD was little, I laid her down in the back seat so I could change her diaper. Put the keys on the seat next to her. Picked her up when I was done, turned & shut the door. *then* realized I had locked the truck, but never picked up my keys. Thank goodness I had her in my arms, and thank goodness for AAA. After that, my mom kept a spare key to my truck on her keyring, and I had a key to her van.
Oh, this was also later in the day that I ran out of gas on the freeway, & my mom had to come rescue me. :-| As in she rescued me, we got to the store, and I locked my keys in the truck.
She still rags on me for it, 9 years later.