CDL Grad needs help

I just graduated a state funded CDL school and am now searching for employment.
The only potential obstacle I have is a Positive Pre employment drug screen for Prime roughly 2 years ago.

My driving/criminal record is spotless this is the only test I have ever tested "positive" on and have taken plenty since.

I notice that most applications ask if you have refused or tested positive in last 2 years.
Does this mean after 2 years I should be free and clear?!

I understand the responsibilities of the job and I take them seriously.