You can ask your primary to order the hair strand testing- however, the PM still may not accept the results.
Was the urine testing sent out to the lab for confirmatory testing/levels testing? Or was this simply an in office screen?
Typically, most PM offices use both- a screen in office, which simply gives a positive/negative result- followed by the urine being sent to a lab for actual levels of the metabolites of the prescribed medications, and how much is in your system. These confirmatory tests look at the mentabolites in your body, giving accurate levels, even if you might be below the in office screening thresholds for a positive result. The lab testing also reveals if you are taking the meds as prescribed.
False positives/negatives with the gc/ms testing done in labs is highly accurate.
As far as requesting a second test now goes, unless a back up testing is done immediately within hrs of a negative result, it is useless as far as correcting a false negative. Too much time has passed, and drs typically dismiss the request and patient.
How many tests have come back negative? It sounds like more than one?
Were you made aware of any other tests not showing the meds? What meds are you taking? How often and when was your last dosing prior to the testing?