It's very easy to get distracted. Plenty of times I've forgotten I had garlic bread in the oven.
Once as a kid, I was making toast for breakfast. I burned two slices. I put two more in the toaster and burned them. By that time, I realized I'd better slow down. I put a single slice in the toaster, which came out okay. When my mom came home from work, she asked, "what happened to all the bread?"