Car Puzzle

On Sunday morning we discovered that the Clio on the drive had a completely flat tyre.  (See extra).  Odd since the tyre had been replaced in February, Martin had washed the cars on Saturday and not noticed it, AND the Clio hasn't moved from the drive for nearly three weeks.  

We wondered if the very hot weather could do this?  (Does anyone know?)

Then tonight, a guy in a white van knocked on the door and asked if I was interested in selling it....!!!???  How weird.  What's that about?

Has anyone else had something similar happen?