Where did the writer receive his friend’s telephone?

An old friend of mine from abroad telephoned from the airport to tell me that he had arrived. I was still at the office at the time. After explaining where my new flat was, I told him that I had left the key under the doormat. Since I might arrive at home rather late, I advised him to go into the kitchen and help himself to food and drink.
   Two hours later my friend telephoned me from the flat in which he stayed. At the moment, he said, he was listening to some of my records after having just had a truly wonderful meal. He had fried two eggs and helped himself to some cold chicken from the refrigerator.
   Now, he said, he was drinking a glass of orange juice. When I asked him if he had reached the flat without difficulty, he answered that he had not been able to find the key under the doormat, but fortunately the living room window just by the apple tree had been left open and he had climbed in. I listened to all this in astonishment. There is no apple tree in front of my living room, but there is one in front of my neighbor’s!