Key will not unlock door to get into truck. Why?

I was sitting in the truck with the ignition off and the doors locked.I went to get out and the alarm sounded.I put the keys in the ignition and turned until the alarm went off but did not start the truck.I got out and locked the doors. Now my keys won't unlock the door to get back in. Key just turns freely when put in. Did something happen and the security system locked me out? How do I unlock the door. No keyless remote