Just please don't PUNISH the poor guy for asking. Unless you had a ring or a picture of your beau on your T-shirt (or even HAD the beau with you on your arm), it probably took that guy a hefty dose of self-talk to even wring up the nerve to ask in a way that was non-creepy non-confrontational and gave you an easy out.

Give him the same respect; if you feel the need to turn down the ride, do so gracefully and honestly and take the offer as a compliment.

-- gnat! (Of all the things we put men through, I don't see any reason to make it worse on them for lack of mind-reading)