What if you insisted you had the key and would prove that you were possibly the owner that way, but when the time came you setup a cardboard door in front of the real one and opened it using a bump key?

That's essentially what has happened with Wright. There are various pieces of evidence that, while not definitive in isolation would be persuasive, which he has insisted he could use to prove himself-- but when the time came he has just been caught faking it over and over again.

It's remarkable that he's been able to continue so long.