If it is simply a true SAMSHA 5 Panel, I can assure you that they only test a morphine
opiate panel. This is where the "extra panels" come along. I can assure you, if you had my 11-panel, you would be failing, but luckily for you, you seem to be sure that it is a basic 5 panel.
So yes, you are safe friend. Given that you have gotten your facts straight, you are fine.
Edit for your sake:
In the crazy case that your body likes to metabolize stuff in the weirdest ways and you start emitting positives on the opiate
category, you can always request the GC/MS lab confirm, which will in fact rule out your false positive. So even if you are afraid of a false positive, they can't confirm it under this panel. So even better for your case I guess.