I Have Been On Methadone For A Few Years Now

I have been on methadone for a few years now cutting down gradually now down to 15 mil. When I went for my monthly prescription at doctors I done a urine sample. I had took my medication 27 hours before and just had a phone call saying there was no methadone in my sample which I do not understand. Since this I have been put on daily supervised as they don,t think I have been taking it. I am very confused as my medicine is stored in a locked cupboard which my wife keeps keys for and gives me it every morning. Can anyone please clarify this for me feel I have been kicked in the teeth while doin so well. My sample was totally clear of prescribed and illicit drugs as I am rebuilding my life thanks.