They've done this to a few workers in my building within the last year or so. Two of the three came back after a couple of weeks and I believe one may still be waiting on his/her test results.
You are likely another employee they didnt want on payroll, profiled you and they pulled the trigger. You weren't the first and sadly won't be the last. To me, this is a moral issue on their behalf. If they cant fire you for being a little behind on a route for whatever reason, then they'll just lie.
I have seen a full time supervisor smoking a joint with part time supervisors in a designated break area outside. I have also seen countless management boot lickers clearly under the influence, one of them even handing over a thc pen to their sup to take a hit WHILE working. You don't have to believe me but I cant unsee these things.
We live in a world where corruption wins. America, corporations, your management team are not exempt from this. They can dehumanize the operations all they want to but in the end, we all pay for the corruption and lies.
I'm sorry that you were most likely profiled. Hope you pass.