I've had a similar experience where I was very consistent with exercise, doing a lot of cardio and weight training almost every day for at least a month. Then I was sick for a week; I could still eat, but didn't go overboard. After that week, I lost almost 5 pounds. I've heard that sometimes the body will "release" water weight or other weight when it rests for a few days. Just don't rest it too often!
It's times like those that I have to remind myself that weight loss is not about the numbers, but about the longterm health benefits, because I'll otherwise go crazy wondering about the fluctuations at the scale!
I wish you a speedy recovery from your injury for continued healthy successes!