Getting Data back from damaged .pages file
The folder was originally a file created in Numbers not Pages.
Since I was given data as a folder with some .iwa files. When I read on internet about opening those files, all posts were regarding Pages rather Numbers. As package contents were same for both formats (.pages and  .numbers) I kept trying opening the folder (by extending .pages) in Pages.
Later on I tried Numbers (giving extension .numbers to folder) and it worked instantly.