(((Cndleflme))) I'm so sorry about your dad.
I found this at
http://www.healthy.net/clinic/lab/labtest/005.asp
Cutoff and Detection Post Dose
The initial screening cutoff level is 300 ng/ml for cocaine and its metabolite benzoylecgonine. Use of cocaine for euphoria may result in positive urines above this level for 48-72 hours post dose. Longer times will be observed in the habituated person using large quantities. The GC/MS cutoff level is 150 ng/ml.
Hope it's helpful.