Was your toast whole grain/ 100% whole wheat? As you know, if it was white bread (simple carb!), that won't hold you as long. Are you drinking too much coffee or other caffeine? I used to take a homeade smoothie with me, made with fruit, ice, 3 scoops of flax seed, and a scoop of protein powder, and fresh spinach---lots of FIBER and PROTEIN, sooo good for you, and YUMMY!
Also, think about bringing some nuts---they are a nice, quick source of protein.....I keep them in the car for those times when I'm very hungry but don't want to eat a meal....good luck!