If you failed twice, there is little you can do. If you are taking the meds exactly as prescribed, typically most PM offices use an in office positive or negative, and then send the test out for confirmatory testing, which looks at actual levels .
It would be highly unlikely that gc/ms testing would be a false negative. It measures the metabolites of the medications in the body.
Did the office just do an in office screen or did they send the urine out for testing? Opana is oxymorphone, which is a synthetic opioid, not a traditional opiate. In office screens have a cut off threshold, which is different depending on the test used. The cut off threshold determines what levels must be present for a positive or negative.
IF they didn't send the urine out for confirmatory testing, then you may be able to get a retest, but even then, depending on how much time has passed it may not help.
I don't know if this will help you or not, but here's an article that lists 15 drugs that can cause a false positive drug test.
A false positive happens in screens in office depending on the test, false negatives are far rarer and are usually sent out for confirmatory testing first.
Did they check off oxymorphone (opana) or morphine on the lab slip? Oxymorphone (Opana) is a semi-synthetic opioid, unlike morphine which is an opiate.
If there was an error is the test request, that could explain the false negative.
Btw, Opana is available in generic form- oxymorphone hcl ER by globabal pharmaceuticals. I know because I take it currently.