Think about it man, the professor said not every secret is told! This was a plan only he could know about, with maybe the son, Rafael. He could only know because it was his only way to keep the crew from folding. Because how can you snitch on something you don’t know, I mean you can tell them it’s lost but they would think you are lying to them anyway. Think about it, the professor is brilliant! He needed to trick his team mind at the end because that was his end game. He panicked because he had to play it off and have everybody help finish off a final plan that they didn’t even know the real meaning to. By him pretending to lose the gold helps put a “fake” new plan in motion only he knew about. The way they threw the police off, like the gold in the ocean and the trucks was all part of his final plan. Just think about it! Rafael owed one to his father because he didn’t want that on his heart and that was his chance to make it right, that’s why the girlfriend asked do you think you will really get your share. Also think about it, would Rafael just plot this whole time not to even move the gold? Was he just gonna leave it buried forever? No that was just part of the whole plan by him holding it and he trusted the former cop to find it! By her finding it and triggering off the invisible alarm was the final piece of the out of the bank part. That alarm brung them back where they could exchange the gold and in the note the professor prolly said thank you or check mate