i actually asked if i could come back and they said they'd have to tell my company that i left. i also was late to my then job because i told them i had an "appointment" i was so glad that i was eventually able to just give them what they wanted
that being said i got nervous myself during a drug test. now i've never done anything but for some reason i just couldn't pee. i had a legit panic attack for a while thinking i was going to lose the job offer (of my current job)