I disagree that the search was illegal. The probable cause seems to be that there was 1 car in a parking lot, kids (most likely underage) nearby drinking, who chose to run rather than stay and talk to the officer. They were obviously doing something wrong, hence they ran.
Sounds like a perfectly legal reason to search a vehicle.
But that's just my opinion.
Sounds like a perfectly legal reason to search a vehicle.
But that's just my opinion.