Stop in for a cup of coffee

Our company had that "injury or accident drug test" kinda mentality. I seen more than 1 fellow employee have a vehicle accident on the clock, go to their alleged drug test and never return or go to the lab. I'm curious how that is handled now that it's legalized.
Only legal in its derivitives here so far.Not sure if my work will can you if those show up. Can the tests even tell the difference? I wouldn't chance it. Last job did 'randoms'. Myself, the manager, one guy in front office got selected multiple times while the goofballs in production that acted like they were on something never did. Hmmm.