First and foremost, are you sure that the vehicle HAS a  supplied spare wheel anyway ?  not such a silly question these days (unfortunately).   Do you have a handbook ?   if the base vehicle is a Fiat ?  have you looked under the L/H cab seat ?   in a RHD vehicle, the passenger seat  ?   it is often stored under there. In my 2012 model in a snazzy large plastic box,  in my 1988 Talbot it was still there but just clipped under the seat.  Good luck !