No reason to worry bout not eating lunch. metabolism is not linked to meal timing or frequency. daily total calories dictate weight gain, loss or maintenance.
Half a small cupcake and a bag of crisps doesnt sound like a lot of calories which could have very easily fit into your daily calorie allotment. the name of the foods you eat has no effect on weight loss, just like frequency.
micronutrients are the major concern with eating "healthy" foods, it has nothing to do with weight so as long as you provide yourself with adequate amounts of protein and fat combined with micronutrients you can eat what ever you want and loss weight as long as you remain in a deficit.
“We are what we repeatedly do. Excellence, therefore, is not an act but a habit.”
"It's not a diet, it's not exercise, it's a lifestyle."