I'm afraid you or your friend is mistaken or misinformed sam as we postal workers don't use SAR's. In fact, the Postal Service doesn't even print an SAR. There is no such thing as a permanent flag. We are not allowed, as part of our job to "notice" what ANYONE gets in the mail much less report it to anyone. We ARE allowed to notice what get's mailed (such as very suspicious boxes) but NOT what gets received. We can get fired for divulging ANY information about your mail to anyone.
Hundreds of thousands of people get their prescriptions filled by online pharmacies. It's not an unusual occurrence for us to deliver prescriptions. Some peoples insurance will pay ONLY if they use a mail order prescription company.