Got a similar story with a trolley.

Was loading groceries and stuff into my car and put down something to stop the trolley from rolling downhill.

Come back from one load and trolley is missing and I see it slowly rolling down picking up momentum in the car park, at the end one incline are more cars parked.

Bolted after the trolley and thankfully no cars were coming up or down the laneway at the time and after 100 metres I manage to catch the trolley without hitting a car or being hit by one.

That scared the bejubus out of me that day. Never parked there ever again.