EPiServer stores orignal parent link in Dynamic Data with store name EPiParentRestoreStore

You can see the view in Database dbo.VW_EPiParentRestoreStore

Code to fetch Original Parent

IParentRestoreRepository parentRestoreRepository

ContentReference parentLink = this._parentRestoreRepository.GetParentLink(deletedItemReference.ToReferenceWithoutVersion());
        if (this._contentProviderManager.IsWastebasket(parentLink))
          return Enumerable.Empty<IContent>();
        IContent content = !ContentReference.IsNullOrEmpty(parentLink) ? this._contentRepository.Get<IContent>(parentLink) : (IContent) null;