Actually, snowy is not correct. Mexicans living in the U.S. can get a TIP good for 180 days and bring a car into Mexico to visit family, etc., and return NOB. My wife has done it.
Your Mexican neighbor came in as a US citizen, not a Mexican, and he came on a visitor permit. Happens a lot, as Mexicans from NOB often want to keep their US cars, and they go back every 6 months.