It doesn't just happen in mental health. We ran into this problem recently when my husband's medical treatment claim was refused by insurance because it was done by the doctor's nurse practitioner rather than the doctor himself. (Apparently the logic that the nurse practitioner does nothing without the approval and oversight of the physician she works under made no difference.) Fortunately for us, the doctor's office acknowledged they were in error in not being sure the nurse practitioner was approved by the insurance company ahead of time and they ate the cost ($1400) -- that's a good doctor's office!