Hitchhiker´s Guide to the Galaxy - Help, Cheats, Hints, How To.

Just wait awhile until Ford Prefect shows up (read the junk mail while you wait). Ford seems a trifle preoccupied with the sky, but he is aware enough of you to try and give you back your towel. Don't take it, or he'll leave and you will be a lot worse off than you ever imagined.

Ahh... Don't take the towel.