I think you're talking about energy you weren't able to measure in an experiment. For your example, the smoke coming off of the burning food was energy escaping that you might not have been measuring. I'm also not an expert on chemistry, but the reactions may have produced chemical energy, where some of the energy was used to synthesize chemicals and is stored in their bonds (not measurable via heat.)

If I'm following the logic properly, you're trying to figure out why your measured energy didn't add up to the calculations you did to predict it, and where that energy went.