I have not heard back about what type of test was done, and the next step would depend upon what test was done.
When performing drug testing, there are screening tests, typically done by immunoassay, and more specific or confirmatory tests, such as gas chromatography/mass spectrometry, or GC/MS.
If the standard screening test for opiates was done, then it would be very common that it would miss oxycodone. The standard test for opiates are good for morphine and closely related compounds, such as heroin
and codeine. However, it is not good at detecting the opiates that are semi-synthetic, such as the oxycodone. In this situation, the appropriate next step would be to request testing specific for oxycodone.
There is an immunoassay screening test for oxycodone, rather than the general screening test for opiates. If this was the test that was done, then it could miss the drug because of a false negative. All of the immunoassay tests have a certain amount of false positives and false negatives. In this situation, the appropriate next step would be to request the confirmatory test, such as GC/MS.
If I can provide any further information, please let me know.