Guessing there was something more that got the thief's attention. After all they're not going to spend days on end watching a house, hoping that something valuble will be randomly dropped off.
I think it was made clear that these thieves just follow delivery trucks around and watch to see what happens when they knock on the door. My hunch is that this is fake and much of the news stories are fake too. I think it's more of a friendly PSA. Mr. OP? I'm not trying to discredit your character but you only have 4 posts, haven't been back for comment and aside from an irresponsible delivery guy we have come up with every logical reason why this shouldn't have happened. I think the only things they will leave is something that can fit in your mailbox or between your entry and screen door.
This kind of stuff has been going on for a while, there have been allegations/speculations that some delivery drivers are in on it; they give accomplices their delivery routes, so that they can be close by, they call or text accomplices the drop off addresses of what looks to be valuable and or where they dropped off and no one was home. In some instances deliberately leaving packages by curbside residential mail boxes instead of walking them to the door so they can easily be grabbed by said accomplices.