I'm confused. Your friend got the script from a doctor, filled it, and then mailed it to you? Had a pharmacy mail it to you? You didn't go to the doc yourself b/c no insurance or... why? Can you just call whomever and find out if it's been sent?
My friend ordered meds over the Internet; they did go through customs. They held them. I don't think she had an honest script, though, and she didn't have a very good experience.
If yours is an honest script, then I'd call and find out what the hold up is. If it's kind of sort of sneaky (even for an A/B) I might not push it. 21 days is a long time, then again, maybe not for an honest med to pass through all it has to. Again, if this is on the up and up, a call should clear it up.