haha, i do that all the time. When i used to work at a theater, i'd get at least one of these comments a day, most people would quickly apologize. Hell, you are bound to see some movies at one point or another working at a theater.
I do that everytime someone tells me happy birthday. I don't know why, it's just a habit.
Hehe, yeah, it has happened to me too... "Enjoy your food!""Yeah, you too.. oh wait..."
Haha I've let that slip out a couple times, I feel like a total dumb ass afterwards of course.
I always do this everywhere.