Aww, that's a bummer! I'm sorry you forgot your fit bit today. I forgot my cell phone when I left for work, then when I got home, I spaced out on taking my heart rate during my work out! Airheadddd.
Everybody forgets things from time to time. Although I don't know what my exact heart rate was, I know for sure that I worked out. Know how? My legs are a little sore. I was definitely pretty sweaty. I feel that wonderful combination of exhaustion and exhilaration that means: I did work!
I bet if you think about it, there are other signals that you had some great fitness minutes today. Regardless of whether or not your little FitBit buddy knows it, your muscles know. Your heart knows. Your lungs know. Your body knows - and that's definitely the most important thing!
Forgive yourself for forgetting, and remember it tomorrow! You still had an awesome day.