Either you didnt take it or the test wasnt a 16 panel drug test. Sounds like maybe you need to ask your dr some ?'s
How long does oxycodone ir 15mg stay in your system if you are taking the med 4 times a day and you took your morning does at 0500 and at 1pm you had a urine screen in your dr office why then would you show up negative for the oxycodone ir?