I think the person will have received the request, even though you have deactivated your account. However, if they try and click through to view your profile the link will be dead. How likely is it that this person will make a deliberate effort to contact your therapist to tell them that they received an apparently random friend request on Facebook, the profile for which is now dead? This is a much bigger deal for you because of your anxiety and dread than it is for anyone else who is associated with the request.