Is it possible that your son WAS tested, but the test came back "negative" , so you were never informed of the results (since I think only those who get "positive" results are usually notified.)

Maddening as it may be, a "positive" or "negative" newborn screen does not necessarily guarantee that a baby does or doesn’t have CAH, though it SHOULD flag those children who are in greatest danger of having an early life-threatening adrenal crisis, usually those with salt-wasting 21-hydroxylase deficiency.

Newborn screening for CAH is based on a baby having very high levels of the hormone "17-hydroxyprogesterone." This hormone is usually most elevated in those with salt-wasting 21-hydroxylase deficiency. So, if your son has 11-oh deficiency, his levels of 17-ohp may not have been sufficiently high for a "positive" result.