As careful as you try to be, anyone who eats out at restaurants that aren't exclusively veg*n restaurants is likely consuming at least trace amounts of animal products unintentionally. It sucks, but that’s unfortunately how it is. Even if you ask your server specifically if something is vegetarian they may not be thinking about things like gelatin, animal rennet, meat stocks is soups and sauces, etc. Back in college I used to eat at a Cornish pasty place that had an item called the "veggie weggie", turns out they used lard in all their crusts so nothing there was vegetarian.