Good morning, have you already been arrested and charged with indirect criminal contempt?
Unfortunately, if she claimed that you violated the pfa and showed any text messages to the police officers, then that's enough to lead to an arrest and criminal charge.
I understand what you are explaining though, is that she actually contacted you first in reference to your son, and the issue is that she was not available at the time you were to return your son to her.
These are all grounds for a valid legal defense. My recommendation would be that you hire an attorney to represent you in this matter, if you haven't done so already, so that all of these defenses can be adequately raised on your behalf at the upcoming hearing.
I hope that helps! Please let me know if you have any other questions. Also, please take a moment to kindly rate me using 3 stars or more, as this is the only way experts are compensated for our time here on 'just answer'. I don't receive a salary here, and am only compensated for my time after you leave me a positive rating. The question won't close after you rate me, so you can still ask follow-up questions after rating me. Thanks so much, I appreciate it!