Had a similar problem a few years ago when I bought a jap import micra for my wife, I ask the dealer at the time to give me a proper size wheel instead of the small yellow wheel, drove away for about 6 months when I noticed that I had a slow puncture, so went to put on the spare only to find that the 4 holes didn’t line up, check the wheel and it had a cut on the side wall (facing down in the boot when I checked first time) and was off a Peugeot 106!
So went straight down to the dealer, gave out to him for giving the wrong wheel and also dangerous wheel. He gave me a proper mirca wheel a apologised for the inconvenience, I would expect a spare wheel (or run flat tyres) to be in every car sold, especially from a dealer. Go back and demand it on safety grounds alone.