Best to ask either your SM or the advancement chair to see what works best in your troop. They can note in your new book that the requirements have been met. You can keep you old book in a safe place in case there are any questions in the future. You should put your completed merit badge blue cards in the same safe place. All this should never be an issue, but remember that almost every body doing the advancement are volunteers with different levels of commitment. Mistakes happen.
Your Council has the originals of all these reports and our troop should also have a copy in the troop files.
I would not count on the originals "held" by council being anywhere findable.
I have been told (by the district advancement people) that our council has moved the responsibility of recording advancement in scoutnet to the troops. So if your troop is not doing that it might not be getting done. Please note that every council is its on entity in this area so what my council does might not be the same as yours.
Venturing Crew Adviser, Assistant Scout Master, Renegade Merit Badge Counselor
Owl-2 WB 92-49
Foothills District Atlanta Area Council
I never teach my pupils. I only attempt to provide the conditions in which they can learn.--Albert Einstein