Can a mother have her baby takin at birth even if she doesnt test positive for drugs at birth of baby?

there is no drug abuse history or anything like that on file she may have messed up 2 days ago and let somebody slip her some crack or a primo ciggerette without knowing now we are worried she will test positive in october is it tru ot only stays 3 days tops in blood and is it possible to test positive in the end of october if she doesnt use which she dont it is sad someone did this to her we will notify her doctor we just want to be prepared for whatever happens..