If the TM's car was still in the lot, the ETL shouldn't have left. You don't leave until all tms are accounted for which includes making sure the number of TMs that clocked out matches the number of vehicles that have left the lot or people's rides you've seen leave the lot. If you still have a mystery vehicle left, you need to be more thorough with the perimeter check unless you've specifically received communication that a vehicle broke down in the lot or some other extenuating circumstance. Best practice is a final for this sort of thing because it could cost target majorly if there was an injury, robbery, or other related incident.