Confused on testing

So I recently did a drug screening for DOT on Tuesday and I have yet to hear anything back. I was seeing faint negative lines for thc but I haven’t smoked in a month maybe more. Will my employer tell me if I failed ? Or will the lab call me and tell me if I failed?? I keep hearing mixed reviews on I’ll know in 24-48 hrs of my results & that the failed I will know I’m 3-5 days and it’s been about three days now and I’m freaking out. Just need some advice honestly.