My waist measurement can vary by up to 2 inches depending on the time of day, time of month, whether I've eaten, etc..
So I don't really trust it, I just look at the trends (just like with the scale). I wouldn't worry about whether the inch that you lost is "real" or not. I'm sure you're moving in the right direction.
“Be not afraid of going slowly, be afraid only of standing still.” -Chinese proverb