submitting to take the test is consent enough for them to send it to the lab. You will only hear of the results if you fail it. They do not have to tell you anthing more than "you need to take a drug test" . I would not ask them if you passed it because that would be an indication that you did drugs and that you may not pass it. Employers assume all employees will pass or at least they hope so.
I'm certain that if you hadn't passed you wouldn't be working right now. Employers need to have employees who are fully aware and practice safety in the workplace. Druggies do not make safe employees and deserve to lose their job to someone who has better command of their personal life.