Ah, you mean buy more normal points. I misread and thought you meant one time use points. New purchased points will have all the rules of those points - assuming they are in their banking window, they can be banked, and while I have no experience with this, I think even if they past the banking window, you could probably get a one-time exception as previous poster mentioned.
So, what will happen here is yes, your borrowed point will not be able to go back, but your new points can be banked as they won't be used for the trip.