Replying to Drug tests for jobs

so i applied to work at my local ski shop and they said i would have to pass a drug test before i could work. i told them i would be able to and took the piece of paper i needed.  they told me to go to some clinic place to get it done, and then they would call me after they got the results.  well i had smoked about 4 days before that so i decided to go to gnc and see what i could find. the guy sold me some stuff that he said would work 100% guarenteed.  i took that and the test about a week later. 

so now for my real question.  does anyone know how long it usually takes for them to figure the results and give them to the employer?  its been a week and like 2 days so far and i havent gotten any kind of call.  also does anyone have any experience with the things you drink from GNC? i cant remember the name but it was one of those detox things.  im pretty nervous right now, because i really want this job.  also does anyone know what an employer would usually do if you failed? would they call and say you failed? what im saying is there any way my parents can find out? 

thanks everyone