The trip home should be fine. Three to four hours in a car will not harm the snake as long as you do not leave it in the car while it is not running. Try to keep the snake warm. After sitting in a display case, it may be a little cold.
The most important thing is to make sure you get a business card and contact information of the vendor at the show. Ask them if they produced the baby. Ask them how often it has eaten and what it has eaten. A good breeder should be able to answer those questions.