Because he didn`t find the home keys.
1-Judys granny lives in a house in the country.
2-Judy and John don`t often visit their granny.
3-Judy and John went to the country on an autumn day.
4-John wanted to watch television.
5-The dog closed the front door.
6-The back door was closed too.
7-John couldn`t open the door.
8-John gave the house keys through the letter-box.
9-Judy`s brother gave his sister the car.
10-Judy went to take the food out of the car.
11-John locked the door again.