Not sure about the Sonic, but many of the newer cars require that the front fascia be completely removed and the base plate takes the place of the bumper frame. If the Sonic has an opening in the front fascia of about 1" to 1-1/2", low down, that's where the connection points of the tow bar will connect to the base plate. Once the fascia is replaced, the base plate and its attaching points are completely hidden.
When I remove my tow bar and attachments, I can't see the base plate connectors unless I get down on my hands and knees and get within a couple of feet of the front of the car.
Hope this helps
Ron