DEAR MISS MANNERS: I used to frequent a coffee shop in the suburbs, where I would work on my laptop for a couple of hours before catching a train to the city. One day, as I was working, a man asked me to keep an eye on his laptop while he took a phone call outside. I agreed, as my train would not depart for another 30 minutes and I assumed the call would be short. As the departure time got closer, the man was nowhere to be found, and his laptop still sat on the counter unattended.