I was thinking the same thing. I was reminded of one of the Indiana Jones movies where I think Indy was beating someone up on a train and when an old couple gave them a shocked look he said something like “no tickets”.
Well they know which cars belong to guests of the resort because they ask you when you check in. At least we always were at Bay Lake, Kidani, Beach Club. And as we rent a car after a few days, we always let the front desk know when we return for the first time.
So it’s possible for Security to check the number plate against the resort records.
And anyone driving into the parking lot has to scan in with a magic band or go through the manual check point. So one way or another, they could identify who has driven into the parking lot and whether they have a right to be there all day.
It may not apply everywhere but all three of those resorts I mentioned have barriers and the same process.