That happened with me. I was dx'ed with cough variant asthma when I was 8, but back then, they were doubting the diagnosis because I never wheezed. I went three years with no asthma problem, except for some bronchitis/pneumonia, and then it came back and now I do wheeze and the asthma is harder to control.
Sometimes people do outgrow their asthma, because it may be reactive airways disease, or because the lungs and bronchi get bigger as the child gets older.