Except, when I returned, I knocked twice and heard Harry whinging... usually a sign that no-one was in. I put my ear to the letterbox and heard the radio faintly playing - a definite sign that no-one was in. So I knocked next door and the neighbour had a front door key. So I walk in... and notice a letter on the hallway floor:
Your keys are next door. Knock for them.
You see, my Nan managed to take this one step further. When we got back, I needed to go to toilet - but just as I was going to, the phone rang. I ran to get it, and it was Nan. I quickly said hi and asked her if she didn't mind me going away quick. She said she had something important to say, though... so I waited. She then told me, FROM THE HOME PHONE, that Cliff had to go out and the front door keys were next door.