Looking for original architectural plans of destroyed condo building

Need original architectural plans for a 1983 building. We recently had a serious fire in one of our units - Jersey Shore, New Jersey. 2/3 destroyed. The unit owner is looking for his upgrades to be covered, but our insurance and by-laws stipulate a rebuild to original architectural specifications. He claims the original buyer (in 1983) had them added to same. We don't have copies of the originals. Need help. Comments on situation and any suggestions as to where to get original plans would be appreciated. TIA