Could codeine cough syrup have shown as morphine at PM?

[Painlife]

I was recently dismissed from my PM prescriber due to morphine showing up in my urine (they send it to a lab). In addition to my prescribed oxycodone and alprazolam, my UA showed positive for morphine, but not codeine. The codeine cough syrup was not prescription, you just have to show ID and sign for it. I had the flue with a hacking, unproductive cough, so I drank the entire bottle during the course of a couple of days.With the syrup not being prescription, I thought nothing of it(I know better now). I know that a percentage of codeine is converted back into morphine during metabolization. I also know that codeine, being the pro drug, will generally clear your system faster and that morphine can hang around longer. Could this be why my UA drug screen, using GS/MS at the lab, showed morphine, but no codeine? What percentage of codeineis metabolized into morphine?

I am waiting for an appointment with a pain management clinic, and I want the doctor to know he can trust me and that I am being truthful. As chronic PM patients, we are so unfairly stigmatized, I don't want this new doctor to refuse to take me as a patient, or refuse to prescribe me my dose of oxycodone that I have been on for years. Life has been hell on Earth since being discharged and I don't want to be refused a working medication at the dose that was effective for me. Can someone please answer my question and provide some insight? I have always been a compliant, trouble-free patient, and I take my medications as prescribed. Thanks to anyone who answers.

[remar]

I'm so sorry this happened to you.
These tests are at best 95% accurate. Your PM Dr should have called you as soon as they got the results so you could take another test.
I would recommend talking to your pharmacist about this because they know how meds are broken down. They also know which meds you can mix with other ones and how a test could come out if certain meds are mixed together. Do some research on your own too. If you find that Codeine can metabolize into Morphine then print it out and take it to your old PM Dr. They should already know these things but you would be surprised at what some of them don't know. Take the information to your new PM Dr too.
I really wish I could be of more help. You said you've been the perfect patient for years, and I believe you have. This happened to my sister one time. We both see the same PM Dr. He called her in to take another test and it was clear. He said he knew it would be because the tests are not perfect.
I agree with you. We're treated like criminals just because we want to try and live a somewhat normal life with less pain. We get urine tests, have to sign an agreement, worry that our tests will come out alright.
I really hope everything just fine with your new PM Dr. Please talk to your pharmacist. You have to sign for the codeine so it's on file. And do some research on your own.