Cookergate

My sister had moved house 4 months earlier, There was a new cooker in this house, but not as good as her old cooker, which she had temporarily left in her old house. She offered to give the cooker she had in her new house to Tracey, the buyer of her old house. For some reason there was a delay in swapping them over. I had visited my sister many times in her new house but for some reason on this occasion I realised that her cooker (to be given to Tracy) looked brand new and asked would it be possible for Tracey to have my cooker and I'd have the new one. This was not a problem. I confirmed that Tracey had not seen the cooker. I asked how she could explain to Tracey that the cooker that was in her house would not be the one she was having. My sister reassured me that Tracey phones her if post arrives and there was no reason for Tracey to visit her house. However, I insisted we think of an explanation, which we did. My sister was sitting facing her front window, 15 minutes later her mouth opened and she looked shocked, yes Tracey was walking down the path.