Replying to Bad

so i failed my pre-employment drug test for the best job ever, beer delivery. its 12.50 an hour from 8-3 and any hour after that is 18.75 monday through friday. the health place already told me and said they will inform my company who basically already told me that the job was mine. i have a starting date and everything. im sure its company policy to not allow me the job however i cant see them not let me ride around in a truck and just carry cases of beer because i had marijuana in my system 1 week after graduation.. idk any thoughts or previous experiences will make me feel more confident for real