[ebg13]

I don't think the key is a strong control without more information about the key.

Say I've lost both a house key and also enough information to, in the current era of scummy personal information aggregation websites, find out my home address, which you can definitely commonly do based on just name and email address and an assumption of local residency. Then regardless of whether I get the key back I should in paranoia change the locks on my house, because now an unscrupulous person who found it easily has a copy of the key and knows exactly where to use it.

So if it's a house key, then in defense it should have no more value to me but has significant (hopefully temporary) value to them.