The Bridesmaids star is on honeymoon in America with his new bride, British journalist and TV presenter Dawn Porter, and they were told the unhappy news by a friend who is house-sitting for them.
They both took to their Twitter.com pages to post pictures and appeal for help tracking down the missing moggy, a Siamese seal-point named Lilu.
The funnyman has even offered a cash reward for her safe return, tweeting, ""Please help find our stupid cat. Went missing in SE (South East) London. Siamese. Blue eyes.... Reward £££""
Porter adds, ""We are on honeymoon and my friend who is taking care of her is very worried and upset, as are we... Where is Ace Ventura (fictional pet detective) when you need him?... I am trying to stay calm. That darn cat!!!... Horrible being away when something like this happens.""