Hello all and thanks for reading

Hello I am a diesel mechanic in Location: NYS due to the type of work I do I need to be approved through FMCSA to work with heavy duty trucks. I got into a low hanging power line during very heavy storms in a work truck and needed to go in for a mandatory drug screening for it. I tried to set up appointments but couldn’t get into one in the timeframe set so I called our hr department and asked if I could have an extension they said it was fine and I would not have any repercussions due to me just not being able to get an appointment. Well I finally got into an appointment and I called my boss after I was done only to be told I was fired due to missing a deadline. Now I cannot get any job that has anything do any heavy machinery work due to missing the federal timeline I didn’t even know was a thing. I wouldn’t even be that worried about it but now I can’t get a job anywhere because of it. I thought it was just my company’s deadline and I was told I would not have any repercussions. This is also on a recorded line what can I do?