As he is an expert burglar himself, this would be quite stupid of him. So it's likely he did it as a joke, as he would have all his really valuable stuff in a safe place, probably elsewhere, so getting robbed would not mean much to him. And maybe also so that his daughter could get in if she ever found out the address.
Answer: Many people do this-hide a house key in an outside place that they think is secure when in fact, most burglars would know to look there.
raywest ★
As he is an expert burglar himself, this would be quite stupid of him. So it's likely he did it as a joke, as he would have all his really valuable stuff in a safe place, probably elsewhere, so getting robbed would not mean much to him. And maybe also so that his daughter could get in if she ever found out the address.