Not In A Right State of Mind
When a lost house key has been found by a stranger, it would probably not warrant a high degree of danger provided that the whereabouts of the respective house are unknown. Unfortunately, a certain individual has posted an advertisement for his lost house keys (including his car’s), which indicates the house’s address. Whether or not this poster is real, then the one who posted it might not be in the right state of mind or was just adding to clout.
It is worth noting that if ever a situation like this arises, the best thing to do is to ask for the services of a locksmith. If you have lost the only set of keys to your house, then there would be no other choice but to replace it, which could be done by a professional locksmith.