Ive heard of false negatives for Oxycodone.
Standard Drug Tests Sometimes Miss Oxycodone
Another problem is that most standard drug tests have a substantial false-negative rate for oxycodone (OxyContin, Percolone, Roxicodone) an opioid drug that's been associated with high levels of abuse. In some cases, a person could be taking oxycodone and the routine drug screen may miss it and report as negative. Oxycodone is also found in the medications Percocet, Roxicet, and Tylox.
Yet one study in the review showed that 88% of doctors didn't know that they may need to order a special test to accurately screen for oxycodone.
that is terrible. I don't know how these things happen
I have, suppose to be clean and oxys showed up in my system even though at that time it had been months since I last used,
There would let me plead my case and I got kick out of rehab