First, let me state I am totally for drug testing in certain aspects of sports. There are numerous drugs that have been proven to give people an edge in specific circumstances and I'm all for curtailing that, it's dangerous and sends a bad message to others.
However… Until there is a test that can identify when the use of the substance occurred and if the person is definitely under the influence of that substance during the test then drug testing will never be an exact science for a sporting event which is why I find it endlessly agonizing that in 2021 it still happens all the time. I live in a legal state(WA) and I smoke a ton, it would take me 2+ months to pee clean but within the next two days after stopping smoking I'd not be under the influence, that's my issue with simply testing for any "drugs" and taking in no account of how slowly or quickly they metabolize… it's just a test fail. That's the system that needs advancements, what someone does in their own free time should have no merit for failing a drug screening for a scheduled event but until there is a reliable way to prove "high during time of testing" it's never going to move forward.
Drugs in your system and being currently high on a substance is a huuuuuuuuge difference. Based on the regulations in place currently you could get a false positive for PCP if you had a bad cold a day before and took a bunch of Cough Syrup that has DXM in it which is standard over-the-counter stuff.
What makes you say you would not be under the influence after two days?