This is difficult to answer. Some community supervision officers will let you know and some wont. Some will just file a Motion to Revoke and let the Court deal with it. Some will address the issue with you before getting the Court involved. Many would not get the Court involved over one failed UA but would address the issue themself.
Your PO may tell you immediately, or may wait to tell you, or may just present the information to the court to get a motion to revoke filed and have you arrested (although this is not likely).
Be certain that you bring a list of all of the OTC medications that you have taken, and DON'T take Nyquil or anything like it that has an alcohol base. It is just not worth the problems it can cause. (9 months is a short time to be on probation. Don't mess it up with excuses that these POs hear all the time about OTC meds.)
This is a question for a Collin County attorney. The rest of us can tell you what the law says and what typically happens where we practice but Collin County is like the twilight zone and you need someone that is there on a day to day basis. Avvo.com has some great criminal defense attorneys that work in Collin County. Do a search and contact their offices to get the real answers to this question.