The booze charges should never have been dropped....
I kind of see this like a fence around a pool or locking up firearms. Sure no one should be on my property in the first place, so therefore they should not drown in my pool. No one should be touching my guns therefore they should not be shot by them. But in those cases I did not take the required due care.
The problem, as I see it is: what is due care? If the keys were in the car but the car was in a fenced in area, is that due care? Keys in the office, office broken into and the car stolen, was that due care? Cars are unlocked, keys for each car are in another unlocked random car on the lot...is that due care? Keys on my kitchen counter, my kid's friend takes them and steals my car later that night from the driveway, is that due care?
Regardless, leaving the keys in an unlocked car is massively negligent on many levels.