The Director doesn't need to find it.

I am here to testify that I saw the map, saw the curved line passing through the Treasury, and saw you destroy what you thought was an incriminating piece of evidence.

It would be much better if you would deal as frankly with me as I have done with you.

Then I shall give you the best advice I can--if my advice will be of any assistance to you." "Yes, and publish it to all the world." "It will have to be published to all the world in any case, for, if I leave here without full knowledge, I will simply go to the police office and there tell what I have learned in this room." "And if I do speak, you will still go to the Director of the Police and tell him what you have discovered." "No, I give you my word that I will not." "What guarantee have I of that ?" asked the old man suspiciously.
"No guarantee at all except my word!" "Will you promise not to print in your paper what I tell you ?" "No, I cannot promise that!" "Still, the newspaper doesn't matter," continued the scientist.

"The story would be valueless to you, because no one would believe it.