I've been reading this site because I took a pre employment DOT drug test. I have been "clean" for 64 days before I took the drug test. I even took an at home drug test and got a light pink line for negative 34 days ago(first void). I thought I was good for sure went in pretty confident. This was 3 days ago. I still haven't heard anything back and after doing research am scared to death now as I find peaple are failing even past 64 days.
I wouldnt get too nervous about this because, under DOT regulations, all urine specimens must be bagged, tagged, and sent off to a seperate facility for analysis - any onsite testing is prohibited, as per DOT regs. And 3 days is hardly enough time for the entire process (courier, analysis, reporting of results) to run its course, considering that there are likely other specimens that have to be tested besides yours.

If you dont hear anything by your prospective employer by Tuesday, 3/12/13, give the employer a call and ask for your "start date" (wink wink). The employers response there oughta shed some light on whether youre good to go, or if the employer had moved on to the next applicant for hire.
During your interactions with the employer, never inquire about the test results. Doing so will only serve to raise suspicious eyebrows, particularly if you want to be viewed by employer as a "drug-free" person.