What drugs do probation officers accept as causing false positives for THC?

I was recently drug tested by my P.O. and all the drug categories were negative. However, she said that the line for THC was "very faint." She accused me of using small amounts of Marijuana. I have never used Marijuana in my life. I just started taking Adderall XR and buspirone. I have seen many sources that indicate Riboflavin (Vitamin B2) and Naproxen may cause false positives for THC. Is there a list or guide where P.O.'s look to see what would constitute a false positive? I have a medical journal that says Naproxen can cause a false positive, and a presription bottle for Naproxen, but could my P.O. just say it is wrong? She told me I was crazy for thinking Riboflavin could cause a false positive. However, why would so many sources say it did? Could it just be a "glitch" in the test? What happens if a test is positive? Is it sent to a lab to test for false positives? I am hoping that if I am accused I will at least get a chance to have the laboratory retest my urine....Please help!