The whole towel ‘thing’ is taken from real life. This is what Douglas Adams said in an interview in 1987:
: “I was holidaying with friends in Greece some years back. Every morning they’d have to sit around and wait for me because I couldn’t find my blessed towel. It seemed to epitomise my disorganised state of being. I came to feel that someone really together, someone who was well organised, would always know where his towel was. I thought of it as a Universal Truth.”