What's the point?
This investigation can end one of two ways:
There's a body there, and it's him:
Meaning: The money was stolen by someone else, and we don't know who. Let's see if we can track any records of their activities to identify and find them.
There is someone else's body there, or they've found a way of faking a body being shipped around the world and buried:
Meaning: He almost certainly was the one to steal the money, and is somewhere else. As his identity is now believed dead, he's not using that identity anymore. Let's see if we can track any records of his activities to identify and find his new identity about which we have no details.
Either way, the answer will be to try to track the person who has access to the stolen funds. It doesn't really matter if we know that it is or isn't him, because whoever it is is going to be hiding somewhere and not announcing their true identity. Until the person is found, nobody can get their money back and no charges can be pressed.