Urinalysis Falability

If you will, picture this scenario.  A  long-time, trusted and visibly disabled patient is under a pain management doctor's care.  He/she is well recieved and liked, having never been the source of any trouble,( i.e losing scrpts, "accidentally" losing narcotic pain meds, or suspicious behavior).  This patient has been rotated to a new around the clock opioid pain med and after two weeks is required to submit a urine sample for testing.  The preliminary test result or instant result, before going to the lab, shows the urine negative for all three different medicines prescribed.  What would a reputable, and ethical doctor do in this circumstance?  Wait for the lab results?  Submit a second urinalysis?  Possibly a serum level test would be more concrete?  Please give me a breif ethics lesson.  Thank you.

[dsmom16]

I'm hoping you get an answer on this, as I was just dismissed from my pain management doctor today for one negative test result (which makes NO sense at all).