Bought a new car this morning

wonder if it had not been filled with gas until you started home with it. I remember an old lady that owned a store down the road from me had a 61 Chevy that she only drove into town every couple of weeks. She would only put enough gas in it to make the trip because she was afraid someone would steal it. She sold the car to a friend of mine and she filled the tank with gas for him. He didn't get but about 3 miles before all the rust in top part of tank