Are there any other medications you've taken recently? Antihistamines(allergy medicines) have been seen to show a false positive for methadone at my clinic. The fact that there are no metabolites should be reason to request another test. That should send up red flags with any lab tech.
What kind of test did they do? Did they dip in the urine or send it out? I see this happening all the time. One person on here put a Journal up describing all the OTC things and some foods that can come up showing drugs that we did not take. BTW I am almost 3 and a half yrs clean off of a 12 yr ride on Methadone. I had some of those test done in the office for other reasons and one came up as POT!! Right, my pot days where way back in the 60s-70s..You can have this taken again and in a much better way.
Bless
Vickie