Refuse to cancel a lost ticket or issue a refund

I've lost a 2 tickets for the Splash water Circus at Computicket on 08/09/17. Immediately went back to my local Checkers and reported lost tickets. Computicket told Checkers that it is their policy not to cancel lost tickets and can't do anything. I then called their customer line myself and the person who assisted me said he cannot do anything but he will try and contact the organisers tomorrow. I was not aware of this policy and in my opinion equates to theft.