If you can, get a hammer and a round flat ended punch about the same size as the head of the bolt and give it a few good clouts on the bolt head with it. This should help to shock the threads loose a bit. Then get a good torx socket and tap (firmly) it into the bolt head. With any luck it should come undone (might still be tight).
If this doesn't work I think the only other way would be for you to strip out the carpet somehow and heat the trapped nut from underneath the car, which should then help to loosen the bolt.