Perhaps the GM was tied up or sidetracked with matters related to the business and simply didnt have the chance to contact you.

If you dont hear anything by tomorrow afternoon, then by all means give them a call first thing Thursday morning and ask for your 'start date'. The employers response there would shed light on whether you are indeed good to go, or if the employer had simply moved on to the next applicant for hire.

Never inquire about the test results. A person who is truly drug-free would never do this because, being drug-free, theres no reason to do so. Doing so would only raise suspicious eyebrows, particularly if you want to be viewed by the company as a "drug-free" person.