In this thread, http://boards.straightdope.com/sdmb/showthread.php?t=799617, I mentioned a short story I read about a time traveller who was spotted because he doesn’t pull his trousers up when he sits down. With linen and other natural fibres they tend to wrinkle if you don’t give them a little pull. But in the future, the synthetic materials are crease resistant.
A few other posters recalled the story, but no-one remembers the name or author. Anyone here got a clue?
The time traveller and the guy chasing him were sat outside at a cafe when this exchange took place if that helps.