Couldn't it also be that NU told Vassar it would honor his scholarship as long as a scholarship exists, but that it could be awarded to someone else at any time? It works that way with walk-ons sometimes--a guy might get an otherwise unfilled scholarship when he's a junior, but loses the scholarship as a senior because it goes to a new recruit.
Yes, that's definitely possible, but again, why keep it a secret?
I hope that's what's going on. It would reflect best on everyone involved.