Couldn't you just go to your boss and "discuss the project" with Jack in the room.
Ask Jack to explain the details of the project and the information that was found. Then, you can go ahead and ask specific questions that you personally know the answers to that Jack won't have a clue what the answer would be.
I have used this method a couple of times to let my teacher/employer know who really did the work and shame the person(s) who took the credit.
EDIT: I just noticed someone else has suggested this method already.
