You know that there are other methods of drug testing, correct? Hair testing, a few different kinds that test fluids in organs, and several different types of urine drug tests. It would have been a better idea to request a retest or pay for one out of your own pocket.

Denial ain’t just a river in Egypt.

If you don't specify which drug you tested positive for, then I'm going to go ahead and say this never happened.

Have you been eating many poppy seed muffins lately?

Could you ask them to do a retest OP? Just to be sure?

Lots of things can give you a false positive. If you don't list over the counter and prescription drugs, you can fail a drug test for not telling them about those. Do some research

I've never failed a drug test before but I assume you could ask for a retest and find out what you tested positive for as well as give the people that are testing you. You should have talked with HR before you quit. Im sure there is a procedure for something like this. Hope you get you job back

Do your friends smoke pot? BC if they've smoked it around you the THC or whatever can remain in your system for up to 23 days even if you didn't actually partake in the the smoking.

Maybe somebody in your workplace wanted your job. Slipped something in your drink, so you would test positive.

Poppy seeds can cause your results to come back positive for opiates. There are trace amounts of morphine and codeine that can be registered in the urine for up to 48 hours after consumption. Eating enough poppy seeds on a bagel or muffin can cause a drug test to come back positive.