If you're not even going through immigration in KL then why would you even get on the flight in the first place? Be sure to let us know how this incredible new life hack works out though
in ancient Thailand, in a dark time few care to remember, the noble warriors of immigration would guard the borders with an iron fist and deadly cunning. Those few they deemed enlightened enough to enter the kingdom, however, would be required to fill in a small piece of card with the details of their return flight and have it stapled to a page in their passport. This, was the legendary TM.6. This, was the arrival card.
Not sure if it will help, but if you have a picture or scan of the page before it got damaged, maybe you can contact immigration first to get a new stamp? No idea of it will help, but it might be worth trying