You know.....as soon as I read this post I started googling this question..."how long after cocaine use during pregnancy, blah, blah"....and you're right. There isn't any definitive information? More than likely they don't WANT to tell expectant mothers a definitive answer, I think. Question must be....do you tell dr so he/she can be prepared just in case, with chance that they'll never know if it goes away in 30 days or something? I'm not sure what to tell you on this one.....your right....it was a dumb idea! Only done once though......I'm not sure what the right thing to do here is? Well, I am, but your not going to want to hear, because I probably wouldn't want to hear it either? Talk to your dr and tell him/her? If the answer is no, the baby won't test positive then I would think that has to stay between you and your dr? If the answer is yes, they will test positive, then your going to get caught when they test your child at birth anyways?
I totally don't envy the position your in, but I will send prayers your way so that you and your baby can get some peace! You know, worrying does nothing other than make us sicker.....especially worrying about things we can't control (I have a special gift for that!!! ) Love and prayers coming your way.