No attorney can tell you for sure whether there was probable cause, unless s/he is retained as your attorney and reviews all the evidence against you. The officer may have stopped you for another reason altogether. You would not know unless and until you receive the police reports. This generally does not happen until after the inital appearance and after the time to hire an attorney.
If the officer truly pulled you over for a u-turn committed 15 minutes earlier, you may have a valid motion to suppress the evidence. I would argue the officer needs some new observations and that the time to pull you over for the u-turn elapsed after he decided to take off the first time.
You may have other defenses you have not even considered. Feel free to contact me directly. I routinely practice in Racine, and I am familiar with the judges and prosecutors there.
I concur with Attorney Missimer's response. If things are as you say, the officer likely did not have reasonable suspicion to pull you over. He may have had reasonable suspicion to pull over the vehicle to ticket your friend for her semi-recent traffic infraction. You will want to get an attorney to discuss the case and bring a motion if the facts are as you remember them and you didn't leave out something important. Good luck.