It is pinned to the wall outside the concrete basement of the bootlegger's shack.
Jesco - I did it!
I killed the old man in his sleep but I can't find the damn key anywhere! You told me it never left his side but I swear it ain't up there!
I'm starting to think this whole damn plan was a mistake. I'm going back to Bog Town to get a damn drink.
If you read this, how about you find the damn key yourself.