If by deleting a Plan from a Plan Set (or matching a Plan to an existing Plan after you already saved the Plan Set, creating Pages...) you cause the Page to be removed/deleted from the project, takeoff and annotation that exists on the affected Page in any Bid within the Project, will be lost, permanently. You are warned any time you perform any action that could cause a Page to be removed from the Project, do not take that warning lightly.
Once a Page is removed from a Project and deleted from all Bids within that Project, the Page can never be restored and anything stored on it, in any Bid in the Project is irretrievably lost.