The Drug Labs usually fax the Probation officers with the results in a few business days of receiving the test in the mail. After that if you in fact tested positive, the PO will normally draw up a VOP affidavit and take it to the judge to sign a warrant for your arrest.
If your probation officer has, or is going to submit a VOP affidavit to the judge, then you need to hire a Lawyer ASAP. Also, know that even if you are being violated you are still on probation, and you have to continue to follow all of the rules of probation. Don't stop going to probation just because you think you already violated. Feel free to call my cell 407-349-7474 if you have any more questions. My office handles VOPs and I'd be happy to give you a free consultation.