You could wait for the cat to return it to you.
Yes, I could, but maybe not! A guy I know locally had £200 in a jar in his house and came home one evening last year to find one of his dogs had knocked it over and eaten all the banknotes. He spent the next couple of days following the dog round closely, collecting and dissecting what 'emerged' to get the pieces of the banknotes. He washed it all off and pieced as much together as he could and sent it off to the Bank of England, who honour to refund the money as long they get the strip with the serial number or some such thing. He ended up getting most of the money back. Patient man!