I don't have a strong opinion about this case, but it would be more correct to compare it to this situation:
You come home one day, entering by the main door as usual, and when going down in the garage you notice the key on the floor with a message saying: "Your garage door were not locked and everybody knew about it, so I came in to take the key on the inner lock, closed it from outside and slipped the key back under the door so nobody else with bad intentions can enter anymore".
In the situation you described I would be pissed off, but not in this one, and IMHO it is closer to this case.
There's the added wrinkle of "... and there's a band of criminals in the area that we know likes to secretly hide in the remote, infrequently used closets of people's houses, where they plot and execute break-ins, thefts, kidnappings, and acts of terrorism."
You come home one day, entering by the main door as usual, and when going down in the garage you notice the key on the floor with a message saying: "Your garage door were not locked and everybody knew about it, so I came in to take the key on the inner lock, closed it from outside and slipped the key back under the door so nobody else with bad intentions can enter anymore".
In the situation you described I would be pissed off, but not in this one, and IMHO it is closer to this case.