Lactose is in a lot of different foods, not just in milk. That’s what’s so nasty about lactose intolerance. It’s in the chocolate bar (milk chocolate). It’s in the creamy pasta sauce. It’s in the coffee-based drink. It’s in mashed potatoes. It’s in pizza. It’s in a lot of breads. It’s sometimes in potato chips, crackers or ramen. Burger King used to use it on their french fries. It’s in a lot of sauces like dips, salad dressings, sometimes even mayonnaise. In Switzerland it’s in the sugary fizzy drinks. Some women have even discovered it’s in their birth control!
Basically, if you didn’t make it yourself, you have to assume it might have lactose in it.