I was talking to a friend at a market yesterday and we were having quite a serious conversation when a man breezed past and said exactly that. I just looked at him (I was shocked that some men still think it's ok to come out with this crap) and he followed up with "you look so miserable" as he walked off.
I'm so pissed off I didn't have a witty put down to hand, so please help me out in case there's a next time (which there inevitably will be)