From my knowledge, only 2 places you may get the "Floor Plan";
1) City
2) Builder
Well, and Designer, the 3rd place which I don't think 90% of us able to have contact.
This is always a good idea to check with city's copy to see what type of house the city was proved for building, and what's the house you see; some of us maybe ... Ha ?!
And this is not part of house inspection

, I believe.
You, the buyer is the one who should ensure you get what you pay for. Check the contract, ALL CONTRACTS.