Find out who the issuing authority is and the badge number. It should be on display.
Report him using it. The council can withdraw the badge from the owner for misuse.
There have been many cases of car crashes where seriously injured people have been removed from the vehicle but the rescue service has failed to see an unconscious baby or small child. "Baby on Board" signs are to alert the emergency services that a child is in the vehicle.
Do you keep your book in a tupperware box?