I wish someone would let you know what is going on. I have a forerunner 35 and just ran 10 miles. It gave me zero steps. Recorded the run and got a badge but no steps. This has happened to me twice in the past week.
If your arm movements were normal for the watch to detect steps (not holding a bottle or pushing a baby stroller, etc.), then sounds like an issue with the accelerometer. Steps are independent of activities. I would try a reset of the watch or contact Garmin Support.
