Hi there ~
I understand your concerns. If you have been smoking
marijuana, the oral swab test does not determine marijuana as far as I know. I do not believe the oral swab was to test for chemicals. I also believe that if you were taking the serum (blood) or the urine tox screen, you will be detected. A hair sample analysis will also detect the marijuana. I also believe that you might need to to consult a psychiatrist
for a letter affirming the fact, if you failed any test but have stopped using, as there are quantitative analysis methods that could determine that you have stopped using over time. And it will also help you treat your withdrawals from the substance.
I hope this helps. Take care of yourself and have a lovely day!