Locked in/locked out

I always fear I'll be locked out of my house, but I never thought my toddler would be the one to lock me out. this morning I was taking a soiled diaper to the trash can(which is 5 steps from our side kitchen door). I closed the door so Brandon wouldn't follow me outside in the blistering heat, but he did follow me to the door and once I shut it, he went up to the knob and turned the lock. This was the only unlocked door in the house so I was locked out. I ran barefoot to my neighbors house to call Paul. The neighbors also called the fire department just in case, but Paul got home with the big red fire truck driving right behind him. While waiting for rescue I stood at the door and talked to Brandon to keep him right there so he wouldn't run off. When I got back from the neighbors he was climbing the stairs and I caught him right before he lost sight of the door. I was so happy we taught him to go up and down the stairs. He climbed down and stayed right next to the door, crying the entire time. He was very upset, he spent 20 minutes in the house crying at the door. I'm so happy Paul works only 15 minutes away, but I am placing a key outside just in case this ever happens again