AG, I do believe it did happen for some Navy candidates last yr. However, if I recall correctly, it happened because they did not get into the school until the RD time frame instead of the ED time frame. Remember, just like universities, they don't expect everyone to accept the scholarship, thus, they over book. I.E. some candidates may apply for multiple SA's and ROTC scholarships. It is a numbers game.
The cadet if I recall correctly did not get accepted to his number 1 school, but got the ROTC scholarship, and then his backup he got accepted to, but did not get the scholarship. I believe he was able to contact them and get it switched, but it was tenuous for him for a few days.
With the Navy and Army you really want to make sure your colleges match up with your ROTC plans, because they are tied together. I would think it is probably also very important to get everything done early, because you don't want to not get a scholarship because there is no room left at the inn.