Taking Two Hydrocodone 10-500 Mg My Wife Tested Positive On A GC/MS For Oxazepam But It Is Impossible?

My wife tested positive on a GC/MS for oxazepam but it is impossible? - taking two hydrocodone 10-500 mg

You do not have that in our house and we all wish the whole time I know if they made something. She received a false positive though. TWICE! She is 40 mg per day Sarafem 1x, 4x daily hydrocodone 10/500, and 3-5x daily uroblue. She was diagnosed with IC or Intercistial cystitis. I fill all the scripts for all medicines and knowledge. Benzodiazepines are not in our house or in your system. The only other med had taken over the last two weeks had been Valium. Does anyone know of pharmocodynamics or pharmokenetic interactions or interactions with other drugs that can give a false positive result for Oxazepam? Please help!