Keys locked in the car!

Locked my keys in the car this morning. Went out and started it and closed the door while I had my morning smoke and coffee. When I went to get back in the freaking doors were locked. Had to ring the door bell to get some one up so I could get my spare keys and open the door. I did not think it was possible to lock the keys in the car while the engine is running? I guess I inadvertinly hit the door lock after I took my hands off the key, however the horn did not sound. Any one else had this happen to them with their Caliber??